Landscape Study of Alternate Light Sources

January 2018

0

sq

FTCoE Contact:

Jeri Ropero-Miller, PhD, F-ABFT

Director, FTCoE

JeriMiller@rti.org

NIJ Contact:

Gerald LaPorte, MSFS

Director, Office of Investigative and Forensic 

Sciences

Gerald.Laporte@usdoj.gov

January 2018

Landscape Study of 

Alternate Light Sources
Landscape Study of Alternate Light Sources

January 2018

Technical Contacts

Rebecca Shute, MS

rshute@rti.org

Ashley Cochran, MS

acochran@rti.org

Richard Satcher, MS, MBA

rsatcher@rti.org

Acknowledgments

We would like to offer our sincerest thanks to Heidi Nichols, CFPH and Detective Sergeant Kyle King, who have 

provided guidance throughout the development of this report and have ensured accuracy and objectivity. Ms. 

Nichols graciously provided photos for this report to demonstrate the use of ALS in a forensic setting.

The authors would also like to thank Dr. Antonio Cantu for his thoughtful review of this landscape report and for 

providing valuable feedback, which we believe strengthens the report. Dr. Cantu was the chief forensic scientist 

for the U.S. Secret Service until he retired in 2007.

Public Domain Notice

All material appearing in this publication is in the public domain and may be reproduced or copied without 

permission from the U.S. Department of Justice (DOJ). However, this publication may not be reproduced or 

distributed for a fee without the specific, written authorization of DOJ. This publication must be reproduced and 

distributed in its entirety, and may not be altered or edited in any way.

Citation of the source is appreciated. Electronic copies of this publication can be downloaded from the FTCoE 

website at http://www.forensiccoe.org/.

Suggested citation:

Forensic Technology Center of Excellence (2018). Landscape Study of Alternative Light Sources. U.S. Department 

of Justice, National Institute of Justice, Office of Investigative and Forensic Sciences.
Landscape Study of Alternate Light Sources

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Table of Contents

Overview of Report.............................................................................................................................4

Introduction to Alternate Light Sources...............................................................................................9

General ALS Product Landscape.........................................................................................................13

Considerations for Selecting an ALS Device........................................................................................15

Types of Devices.........................................................................................................................................16

Device Considerations ................................................................................................................................17

ALS Applications.........................................................................................................................................20

Crime Scene Investigation ..................................................................................................................................20

Crime Laboratory ................................................................................................................................................24

Forensic Biology Unit.......................................................................................................................................24

Latent Print Unit..............................................................................................................................................28

Trace Evidence Unit.........................................................................................................................................32

Other Applications..............................................................................................................................................33

ALS Photography ........................................................................................................................................34

ALS Device Education..................................................................................................................................36

Featured ALS Product Landscape.......................................................................................................37

Selected Single-Wavelength ALS Devices.....................................................................................................38

Selected ALS Multiwavelength Units...........................................................................................................39

Summary ..........................................................................................................................................42
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Overview of Report

The National Institute of Justice (NIJ)’s Forensic 

Technology Center of Excellence (FTCoE) at RTI 

International (RTI) directed this landscape study of 

alternate light sources (ALS) with input from industry, 

law enforcement, forensic, and criminal justice system 

communities. 

A landscape study provides a comprehensive overview 

of market participants, their products, and product 

features to enable end users to make informed 

purchasing decisions. This report gives an overview of 

currently available ALS for crime scene processing and 

laboratory applications.

This document provides decision makers and end users 

such as laboratory directors, crime scene investigation 

unit personnel, forensic photographers, and other 

stakeholders with the following: 

• Background information on ALS, the available 

products and manufacturers, and applications 

for which this technology can be used.

• Input from current users to inform potential 

technology adopters about implementation 

considerations for ALS, including device 

performance, applications, and education.

• A comparison of the features and capabilities 

of ALS instruments. 

• Cases illustrating successful adoption of ALS 

technology. 

This report also offers important considerations for 

decision makers purchasing for either field or 

laboratory settings. While multiple applications for ALS 

in forensic science exist, these applications represent 

scenarios in which ALS is most commonly used based 

on interviews from field experts. 

Landscape Study of ALS

ALS examples featured in this report emit light in the 

visible and ultraviolet (UV) region of the

electromagnetic (EM) spectrum. These sources cause 

certain materials to fluoresce, which enhances the 

ability to visualize specific evidence during searches 

and examinations in the field and laboratory. Evidence 

illuminated by these light sources can be visualized by 

the eye using an appropriate barrier filter or 

documented using a standard digital camera equipped 

with an appropriate filter. Other ALS technologies exist 

in the market, such as reflected ultraviolet imaging 

systems (RUVIS) and infrared imaging systems. These 

technologies require specialized cameras or imaging 

systems to visualize and document evidence and are 

beyond the scope of this report. 

Alternate light sources are available for purchase from 

over 10 manufacturers. The FTCoE interviewed 21

experts across multiple forensic science disciplines and 

chose to highlight six instruments consistently 

referenced by these experts. It is important to note that 

the FTCoE is not recommending any one instrument 

over another. Our goal is to present a broad scope of 

ALS functionalities and applications. The FTCoE 

suggests considering and potentially testing a variety of 

ALS devices to ensure an agency’s specific needs are 

met.

This FTCoE landscape study of ALS provides: 

► Agencies a better understanding of the types 

of devices available and recent advances in 

ALS technology.

► User profiles that offer the insight of past 

experiences with ALS devices to help 

agencies make informed purchasing 

decisions.

► Emphasis on the value of training ALS users 

and available training resources.
Landscape Study of Alternate Light Sources

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While the content of this report has been developed from interviews with over 20 stakeholders, the experiences of 

six different agencies using ALS devices have been explicitly profiled. Spread amongst the United States, these 

interviewees provide insight for both crime scene and laboratory applications.

Research Methodology 

To conduct this landscape study, the FTCoE used a 

process that included the following steps: 

• Researched secondary sources—including 

journal and industry literature—to obtain 

information related to ALS capabilities, 

successful use cases, and procurement 

considerations for the devices. 

• Discussed state-of-the-art ALS technology with 

subject matter experts, including crime scene 

and laboratory practitioners, technology 

developers, and key decision makers. 

• Attended ALS photography course to better 

understand the technology, obtain firsthand 

user experience with the devices, and discuss 

technology with users. 

• Documented, summarized, and released key 

findings to the forensic community. 

UV Fluorescence Versus Reflected-UV 

Imaging: What’s the Difference?a

► UV Fluorescence (Focus of this report): UV 

can excite electrons in a material, causing 

it to fluoresce. This emitted light is at a 

longer wavelength and lower energy than 

UV, and falls within the visible light range. 

As a result, UV fluorescence is visible to the 

naked eye and standard digital cameras. 

► Reflected-UV Imaging (Not in this report):

Reflected-UV imaging is possible when UV 

reflects off an object and is captured by a 

camera that is UV-sensitive.

aRichards, A., & Leintz, R. (2013). Forensic Reflected Ultraviolet 

Imaging. Journal of Forensic Identification, 63 (1), 48-69.

Retrieved from https://www.theiai.org/member/jfi/JFI-2013-1-

46.pdf

 
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Subject Matter Experts and Stakeholders

We would like to thank the various forensic science community stakeholders and practitioners who offered insight, 

analysis, and review.

Jennie Ayers

Crime Scene Coordinator, Latent 

Print Section, Idaho State Police;

Meridian, ID

Adam Becnel 

Crime Laboratory Manager, 

Louisiana State Police; Baton 

Rouge, LA

Keith Breeding 

Business Manager, Rofin Forensic; 

Oakland, CA

Lieutenant Peter Cestare

Commanding Officer, Crime Scene 

Investigations Unit, Horry County 

Police Department; Conway, SC

Penny Dechant

Technical Lead, Latent Print Unit, 

Arizona Department of Public 

Safety; Phoenix, AZ

Jenny Elwell

Forensic Scientist Supervisor/

Special Agent, Forensic Biology 

Division, North Carolina State 

Crime Laboratory; Raleigh, NC 

Detective Richard Emmons 

Special Investigations Unit, 

Snohomish County Sheriff’s Office; 

Snohomish County, WA

Erin Forry

Criminalist IV/Quality Manager, 

Crime Laboratory, Boston Police 

Department; Boston, MA

John French 

Administrative Supervisor, Crime 

Scene Unit, Forensic Service 

Division, Baltimore Police 

Department; Baltimore, MD 

Walter Hiller

Forensics Instrument Specialist, 

SPEX Forensics; Edison, NJ

Debra Holbrook, RN, SANE-A, FNEA/P

Forensic Nurse Coordinator, 

Mercy Medical Center; Adjunct 

Faculty, Institute for Johns 

Hopkins School of Nursing; 

Baltimore, MD

Detective Sergeant Kyle King

Crime Scene Unit Supervisor, 

Criminal Investigations Section, 

Indian River County Sheriff’s 

Office; Vero Beach, FL

Dr. Emma Lew, ME

Director, Miami-Dade County 

Medical Examiner Department 

Miami, FL

Dr. Marilyn Miller

Associate Professor, Virginia 

Commonwealth University; Chair, 

OSAC Crime Scene Investigation 

Subcommittee; Richmond, VA

Heidi Nichols, CFPH

Senior Forensic Photographer, 

Miami-Dade County Medical 

Examiner Department, Miami, FL

Doug Peavey 

President, Lynn Peavey Company; 

Lenexa, KS

Larry Stringham

Forensic/Evidence Supervisor, 

Cape Coral Police Department; 

Cape Coral, FL

David Tobin

President, Foster + Freeman; 

Sterling, VA

Dr. Tatiana Trejos

Assistant Professor, Department 

of Forensic and Investigative 

Science, West Virginia University; 

Morgantown, WV

Dr. Christian Westring

Director of Criminalistics, Quality 

Manager; NMS Labs; Willow 

Grove, PA

Lieutenant Scott Youngblood

Technical Lieutenant, Forensics 

Investigation Center, New York 

State Police; New York, New York
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Glossary of Commonly Used Words and Phrases 

For the purposes of this document, the following terms are defined: 

Alternate light source (ALS): a tool used to help 

visualize evidence that is not apparent to the naked 

eye. ALS typically utilize the UV and visible light 

spectrum. Also known as a forensic light source (FLS).

Alternating current (AC) power: a type of power supply 

where the electric current cyclically changes direction. 

AC power is the type of power delivered to houses and 

businesses and is utilized by plugging appliances into 

wall sockets.

Bandpass filter: an optical filter that blocks 

transmission of light both above and below a certain 

wavelength range. Bandpass filters are used to filter 

light to specific wavelength ranges within the alternate 

light source. 

Barrier filter: an optical filter that blocks transmission 

of light either above, below, or between a specific 

range of wavelengths, which permits certain 

wavelengths to reach the eye or other detector. 

Brightness (of light): a measurement of the level of 

intensity of a light output from a light source. This can 

be measured in lumens. In this report, the term 

“intensity” is used as a proxy for brightness. 

Ecchymosis: discoloration of the skin due to ruptured

blood vessels and resulting blood leakage into 

subcutaneous tissue.

Electromagnetic (EM) spectrum: the complete range 

of wavelengths of electromagnetic radiation. This 

spectrum includes visible light (red, orange, yellow, 

green, blue, indigo, and violet) as well as non-visible 

radiation (ultraviolet and infrared radiation, radio 

waves, x-rays, and gamma rays).

Electromagnetic (EM) radiation: a type of energy that 

travels as both a wave and a particle. Waves of 

electromagnetic radiation are made up of oscillating 

magnetic and electric fields. Visible light is a type of 

electromagnetic radiation. 

Emission wavelength: the wavelength of light emitted 

by a fluorophore when it changes from an excited state 

to a ground state. This wavelength of light is visualized 

as fluorescence.

Excitation wavelength: the wavelength of light that 

causes a fluorophore to transition to a higher energy 

level, or excited state.

Excited state: the state in which an atom or molecule 

has more energy relative to its ground state; a higher 

energy level.

Fluorescence: a phenomenon in which light is emitted, 

resulting from the excitation of a fluorophore; 

absorption of a shorter wavelength followed by 

emission of a longer wavelength.

Fluorophore: a molecule that emits light in the form of 

fluorescence upon excitation.

Forensic light source (FLS): see alternate light source 

(ALS).

Frye standard: a standard of admissibility of evidence 

based on the ruling of Frye v. United States in 1923, 

which dictates that expert testimony must be based in 

established scientific methods generally accepted 

within the relevant scientific community. 

Frye-Reed hearing: refers to a Frye hearing in 

Maryland, named after the first case that extensively 

discussed the Frye standard, Reed v. State.

Ground state: the lowest energy state of an atom or 

molecule.

“Hot spot”: an area within the light beam emitted from 

an ALS that is brighter than around the light beam; a 

hotspot is usually observed in the center of the light 

beam. Refer to Figure 5 for an illustration of a hot spot.
Landscape Study of Alternate Light Sources

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Incandescent light: a light source that produces 

illumination through the heating of a filament such as 

tungsten, which emits radiation in the visible and 

infrared (IR) region of the EM spectrum. 

Infrared (IR) radiation: that part of the EM spectrum 

whose wavelength is above 700 nm usually below

12,000 nm.

Light Absorption: a process by which light strikes a 

surface, causing the material to absorb energy and 

transition to a higher energy state. 

Light emitting diode (LED): a device made from a

semiconductor material that emits light when an 

electrical current is passed through it. 

Longpass filter: a barrier optical filter that blocks 

transmission of light below a certain wavelength range. 

Light with a longer wavelength (and lower energy) is 

perceived by the viewer. 

Multiwavelength device: an ALS that emits more than 

one peak wavelength of light.

Peak wavelength: the wavelength of light that is most 

apparent; most of the light emitted by the ALS is at this 

wavelength. 

Photon: an elementary particle of visible light. 

Shortpass filter: a barrier optical filter that blocks 

transmission of light above a certain wavelength range. 

Light with shorter wavelength (and higher energy) is 

passed onto the viewing area.

Sensitivity: the precision of the range of wavelengths 

of light emitted from the ALS device; devices 

considered to be more sensitive emit light at a more 

narrowly focused wavelength range.

Single-wavelength device: an ALS that emits a single 

peak wavelength of light. For the purposes of this 

report, this term refers to a device that emits a small 

range of wavelengths surrounding the peak 

wavelength. For example, a blue light may emit a peak 

wavelength of 475 nanometers (nm), but also emit light 

in a small range around that peak wavelength (465-485

nm). This same device is incapable of emitting other 

ranges of light. Lasers, which emit light at a singular 

wavelength only, are not included in this report. 

Ultraviolet (UV) radiation: that part of the EM 

spectrum below 400 nm and usually above 200 nm. 

Visible light the part of the electromagnetic (EM) 

spectrum that is visible to the human eye. Visible light 

ranges from approximately 400-700 nm. Occasionally 

in this report the term “visible spectrum” is used to 

mean the more correct term “the visible region of the 

EM spectrum.” The same occasionally occurs with the 

term “UV and IR spectrum” which more correctly 

means “the UV and IR region of the EM spectrum.” 

Furthermore, the term “light” strictly applies only to 

the radiation of the visible region of the EM spectrum, 

but in this report the term “light” is occasionally used 

for radiation of the UV region and of the IR region of 

the EM spectrum.

Wavelength: a measure of the distance (nm) between 

two consecutive peaks (or troughs).
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Introduction to Alternate Light Sources

Fluorescence

Alternate light sources (ALS) enhance the visualization 

of evidence not readily apparent to the naked eye, 

facilitating collection, documentation, and processing 

of evidence. The technology uses light emitted at a 

controlled range of wavelengths to improve the 

contrast of evidence against a background. Alternate 

light sources that emit light in the visible range (400–

700 nanometers [nm] within the electromagnetic 

spectrum) cause multiple types of evidence to be 

visualized through fluorescence. 

Fluorescence is the emission of light of a longer 

wavelength by a substance that has absorbed light of a 

shorter wavelength. When a fluorophore, or molecule 

capable of fluorescence, is subjected to a light source 

at a specific wavelength (called the excitation 

wavelength), it absorbs energy and transitions into a 

higher-energy excited state. Shortly after light 

exposure, the molecule returns to its normal state, or 

ground state, and the excess energy is emitted as light. 

This wavelength of light (called the emission 

wavelength) is of a longer wavelength than the 

excitation wavelength, and is detected as 

fluorescence.

1

Some types of evidence important to a crime scene 

investigation—such as hairs, fibers, or biological fluids

 

1

Johnson, I., & Spence, M.T.Z. (Eds.) (2010). Molecular Probes Handbook, 

A Guide to Fluorescent Probes and Labeling Technologies (11th ed.). Life 

Technologies Corporation.

2 SPEX Forensics. Forensic Light Source Applications: Wavelengths and 

Uses. Retrieved from 

that may contain DNA—naturally fluoresce when 

excited by a certain wavelength or range of 

wavelengths. Developing agents applied to evidence 

such as fingerprints may also fluoresce with 

illumination. ALS devices in the visible spectrum emit 

light at different colors, which are controlled ranges of 

visible light wavelengths with specific peak 

wavelengths (most of the light emitted by the device is 

at this wavelength). Figure 1 shows the types of 

evidence that can be detected at specific wavelength 

ranges (colors of light).

2 Table 1 gives the general 

wavelength ranges for each color of visible light.

3

http://www.horiba.com/fileadmin/uploads/Scientific/Documents/Forensi

cs/fls.pdf

3 Nichols, H., & Sanfillippo, P. (2017) Alternate Light Source Workshop: 

Course material. Tritech Forensics. St. Louis, MO, June 26-27, 2017.

Fluorescence Versus Light Absorption

Some evidence—such as untreated blood and 

some treated fingerprints—absorbs the light

emitted by ALS and may not fluoresce. Though 

these types of evidence may not fluoresce, 

illumination of evidence still enables easier 

detection and documentation via 

photography. However, fluorescence of 

evidence is more common than absorption.
Landscape Study of Alternate Light Sources

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Figure 1. Examples of evidence types detected using different wavelengths of light in the visible spectrum. The evidence and wavelengths 

listed in this figure are not exhaustive.

 

Table 1. Wavelength ranges correlated to visible colors of light 

emitted by ALS, and ultraviolet light. These ranges are 

approximate.4

 

4 Nichols, H., & Sanfillippo, P. (2017) Alternate Light Source Workshop: 

Course material. Tritech Forensics.

Barrier Filters

Visualizing and documenting evidence by ALS 

illumination requires use of a barrier filter. During the 

fluorescence process, light emitted by the ALS (at the 

excitation wavelength) is reflected back to the eye, 

overpowering the emitted fluorescence (at the 

emission wavelength), often rendering it undetectable. 

Barrier filters enable visualization of fluorescence by 

preventing transmission of light at the same 

wavelength as the excitation light to the eye or 

detector (such as a digital camera).

5

Light produced by 

the fluorescing compound passes through the barrier 

filter and is detected by the eye or camera. Figure 2

demonstrates the role of a barrier filter in visualizing 

evidence. Barrier filters are manufactured in the form 

of goggles, flat viewing panes, and filters for digital 

cameras—any combination of the aforementioned 

barrier filters and detectors can be used with single and 

multiwavelength units. The appropriate barrier filter 

depends on the wavelength of light used; for example, 

evidence illuminated by blue light can most often be 

5 Marsh, N. (2014). Light as a Forensic Photographer’s Tool. In Forensic 

Photography: A Practitioner’s Guide (1st ed.) (pp 163-193). River Street, 

MS: Wiley & Sons.

Wavelength Range (nm) Color of Light

630–700 Red

590–630 Orange

560–590 Yellow

490–560 Green

450–490 Blue

400–450 Violet

260–400 Ultraviolet (invisible)
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visualized through an orange barrier filter. Without 

these filters, the illuminated evidence would most 

likely be undetectable to the naked eye.

In most circumstances, the barrier filters used for ALS 

that emit visible light are longpass filters. These optical 

filters block transmission of light with wavelengths 

below a certain range. Light with a longer wavelength 

(and lower energy) cannot be perceived by the viewer. 

When the appropriate color barrier filter is used, it can 

effectively block the excitation light emitted by the ALS.

Barrier filters must transmit precise wavelengths of 

light to effectively detect evidence. Filters that block 

light transmission at a defined wavelength range may 

more reliably block the transmission of ALS excitation 

light, enabling better visualization of evidence. This 

means that undesired wavelengths of light are less 

likely to “leak” through the barrier filter, obscuring the 

fluorescence. Figure 3 demonstrates the importance of 

barrier filters with a semen stain illuminated by blue 

light and visualized (a) with and (b) without an orange 

barrier filter. 

Figure 2. This figure depicts how a detector perceives fluorescence of evidence when using an ALS and a barrier filter, using blue light as an 

example. Note that the barrier filters and detectors are interchangeable regardless of light source used. Steps in process: 1) Blue light is 

emitted from a single wavelength or multiwavelength ALS unit. 2) The light hits the surface of interest, which can be multiple types of 

evidence. A fluorophore absorbs the energy and transitions into the excited state. 3) Light of a longer wavelength (orange) is emitted when 

the fluorophore returns to its ground state. Both the initial blue light (excitation) and orange light (emission) are reflected off the surface. 4) 

The use of an orange barrier filter—whether a pair of goggles or a lens filter—allows only orange light to pass through to the eye or camera, 

leading to better visualization of the detected stain. 
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Barrier and Bandpass Filters

Though bandpass and barrier filters have different 

functions, they operate using the same principles. 

The bandpass filter within the ALS device allows 

wavelengths within a certain range to illuminate the

evidence, while the barrier filter is used in 

conjunction with the light source so that the user can 

visualize the fluorescence emitting from the 

illuminated evidence.

Figure 3. (a) Semen stain illuminated by blue light (475 nm) and visualized with an orange barrier filter, and (b) semen stain illuminated by 

blue light (475 nm) without an orange filter. The reflected blue light in (b) overpowers the fluorescence of evidence, whereas the blue light is 

blocked by the orange barrier filter in (a).

Light Source Technologies

Just as there are various types of barrier filters, there 

are a variety of ALS technologies on the market. ALS 

devices are generally powered by three different types 

of light sources:

• Incandescent bulbs

• Arc lamps

• Light-emitting diodes (LEDs).

Incandescent light bulbs produce illumination through 

heating a filament, which emits radiation in the visible 

light spectrum. This light is composed of energy at all 

wavelengths within the visible light spectrum, and is 

emitted as white light. Many ALS devices use 

incandescent bulbs that are filled with xenon, while 

others are filled with halogens or metal halides.

6 Some 

light sources use arc lamps, which emit light when a 

charge is passed through two electrodes in a bulb 

pressurized by a gas, such as xenon.

To operate as an ALS and emit light at discrete 

wavelength ranges, units powered by incandescent and 

arc lamp bulbs must be outfitted with bandpass filters, 

 

6 Norman, M., & Buszka, J. (2013). UV and Narrowband Visible Light 

Imaging. In Alternate Light Source Imaging: Forensic Photography 

Techniques. (pp 25-61). New York, NY: Taylor & Francis.

7 Marsh, N. (2014). Light as a Forensic Photographer’s Tool. In Forensic 

Photography: A Practitioner’s Guide (1st ed.) (pp 163-193). River Street, 

MS: Wiley & Sons. 

which allow light in a certain range of wavelengths to 

pass through. The smaller the range of wavelengths 

that can pass through the filter, the higher the quality 

of the filter; generally, these filters allow a range of 40–

50 nm to pass through. ALS devices powered by 

incandescent and arc lamp bulbs—depending on the 

ranges of bandpass filters incorporated—can be tuned 

to any color or range of wavelengths. This positions the 

devices to serve as effective multiwavelength units.7

LED-based ALS devices, on the other hand, emit light in 

a small range of wavelengths viewed as one color. The 

color of light emitted by LEDs is based on the 

combination of semiconductors incorporated into the 

light source.

8 Because LEDs emit light only in a small 

range of wavelengths (on average, over a 30–50 nm 

range), this technology is most often used in singlewavelength ALS flashlights.

9

8 Office of Energy Efficiency & Renewable Energy, Department of Energy. 

LED Basics. Retrieved from https://energy.gov/eere/ssl/led-basics

9 Marsh, N. (2014). Light as a Forensic Photographer’s Tool. In Forensic 

Photography: A Practitioner’s Guide (1st ed.) (pp 163-193). River Street, 

MS: Wiley & Sons.

(a) (b)
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Table 2 continued on next page

General ALS Product Landscape

The market for ALS devices is quite large, with over 15 manufacturers and 50+ products available. This section 

provides a general product landscape for ALS on the market, and provides an overview of selected manufacturers 

and products specifically referenced in user interviews (Table 2). 

General Product Table 

Table 2. An overview of ALS manufacturers and devices on the market. Note that this list is not exhaustive.

Footprint Wavelength Power Bulb Wavelengths Available

Manufacturer Instrument Flashlight or 

Unit

Single, Dual, 

Triple, or Multi

AC, Battery, 

Rechargeable 

Battery

LED, 

Incandescent, or 

Arc

White

Red

Orange

Yellow

Green

Blue-Green

Blue

Violet

UV

http://crimesciencesinc.com/

Glowtorch Forensic 

Light Sources Flashlight Single Rechargeable Battery LED       

Illumacam-2 Unit Dual Rechargeable 

Battery LED    

http://www.caogroup.com/ultralite.html

ALS Ultralite Unit Multi Rechargeable 

Battery LED      

https://www.shopevident.com/

ORION-LITE 455nm 

Blue Light Flashlight Single Battery LED 

ORION LITE 3-Piece 

Light Kit Flashlight Single Battery LED   

http://www.fosterfreeman.com/

CrimeLite 42S Flashlight Dual

AC or 

Rechargeable 

Battery

LED       

CrimeLite 82S Flashlight Single

AC or 

Rechargeable 

Battery

LED        

CrimeLite 82L Unit Dual

AC or 

Rechargeable 

Battery

LED  

CrimeLite XL Unit Multi

AC or 

Rechargeable 

Battery

LED    

CrimeLite 2 Flashlight Single

AC or 

Rechargeable 

Battery

LED        

https://www.foxfury.com/

Hammerhead Flashlight Single Battery LED    

Scout Light System Flashlight Single Battery LED  

MF-1000 Flashlight Multi Rechargeable 

Battery LED    

Rook NDT Flashlight Single Battery LED 

OPTIMAX 450 Flashlight Single Rechargeable 

Battery LED 
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Footprint Wavelength Power Bulb Wavelengths Available

Manufacturer Instrument Flashlight or 

Unit

Single, Dual, 

Triple, or Multi

AC, Battery, 

Rechargeable 

Battery

LED, 

Incandescent, or 

Arc

White

Red

Orange

Yellow

Green

Blue-Green

Blue

Violet

UV

https://spexforensics.com/

(a division of HORIBA)

CrimeScope Unit Multi AC Arc         

Mini-CrimeScope Unit Multi AC Incandescent        

Handscope LED Unit Multi

AC or 

Rechargeable 

Battery

LED    

HandScope Xenon Unit Multi AC or Single-use 

Battery Incandescent        

Focus LED Flashlight Single Battery LED     

http://labino.com/

TrAC Finder Flashlight Single Rechargeable 

Battery Incandescent 

Labino Astra Crime Kit Flashlight Single Battery LED       

Labino Nova Crime Kit Flashlight Single Battery LED       

http://www.lumatec.de/en/

Superlite S04 Unit Multi Rechargeable 

Battery Incandescent

Superlite 400 Unit Multi Rechargeable 

Battery Incandescent         

Superlite M05 Unit Single Rechargeable 

Battery LED        

https://www.x-loupe.com/

AgileLite System Unit Single Rechargeable 

Battery LED      

Portable Microscope 

Camera System Unit Dual Rechargeable Battery LED   

https://www.lynnpeavey.com/

BattleLite Flashlight Single Battery LED   

https://www.nebotools.com/

CSI Quatro Flashlight Triple Battery LED   

http://www.rofinforensic.com.au/

Polilight PL500 Unit Multi AC Arc         

Polilight PL400 Unit Multi AC Arc      

Polilight Flare Plus2 Flashlight Single Rechargeable 

Battery LED         

Poliray Unit Multi AC Incandescent         

http://www.sirchie.com/

Bluemaxx Forensic 

Light Source Flashlight Single Battery Incandescent  

Forensic Alternative 

Light Source 3000 Unit Single Rechargeable Battery Incandescent      

megaMaxx 3-Watt 

Alternate Light System Flashlight Single Battery LED        
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Considerations for Selecting an ALS Device 

Though the process of investigating a crime scene ultimately varies by case and by jurisdiction, multiple 

stakeholders are involved. The general steps and personnel in a crime scene investigation are shown in Figure 4, 

with some example considerations for use of ALS in crime scene processing: 

Figure 4. Crime scene investigation procedure, key personnel, and ALS considerations for each step of the process. 
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As agencies and laboratories look to implement or

replace their equipment, they must select the 

appropriate device from a crowded ALS market. Over 

10 manufacturers sell more than 50 products combined 

that range in price from $20 to $20,000. Today’s ALS 

products incorporate more advanced technologies—

such as LEDs, compact packaging, and precise bandpass 

filters—to improve the user experience, which 

ultimately leads to better detection and investigative

outcomes. This section reviews ALS product types, 

features, applications, and education to help agencies 

make an informed decision when purchasing an ALS 

device for their specific needs.

Types of Devices

Two main types of ALS exist: 

• Devices that emit only one specific 

wavelength and

• Devices that emit multiple wavelengths to 

scan for evidence.

Each device type possesses benefits and limitations 

applicable to most ALS applications; Table 3

summarizes this information. Single-wavelength ALS 

devices are typically handheld, battery-powered 

flashlights. These products use either incandescent 

light or LEDs. Some single-wavelength ALS products 

consist of one discrete flashlight per wavelength, while 

others have one flashlight and interchangeable heads 

with different wavelengths. These flashlights can be 

sold individually, as a set that contains multiple 

flashlights, or as a set that contains interchangeable 

flashlight heads. 

Multiwavelength ALS devices are typically larger 

devices that produce light at a variety of wavelengths 

over the visible light spectrum (and in some cases UV). 

Most multiwavelength devices operate using an 

incandescent bulb—such as a xenon bulb—which 

produces a white light that is filtered by a bandpass 

filter. However, some multiwavelength products on the 

market use multiple colors of LEDs in the same device. 

Typically, multiwavelength units must be plugged into 

a power source to operate. In most cases, these devices 

emit 5-16 different wavelengths of light; fewer devices 

on the market emit two or three colors of light in a 

smaller device. Refer to Table 2 (General Product Table)

for more information.

Expert interviews revealed that multiwavelength 

devices tend to stay in the crime laboratory, especially 

in circumstances where the crime scene does not have 

available or reliable power sources. Single-wavelength 

units, however, are consistently used in both the field 

and the laboratory setting. They provide value in the 

field because they operate without outlet power and 

are small, light, and easily portable. In the laboratory, 

single-wavelength ALS devices provide easy 

maneuverability and freedom from cords that could 

pose a safety hazard in a darkened environment. 

Single-wavelength ALS devices have comparable 

intensity to multiwavelength units. Because individual 

single-wavelength devices typically cost less than 

multiwavelength units, purchasing flashlights at one or 

two selected wavelengths offers an economic 

alternative to purchasing a more expensive 

multiwavelength device.
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Table 3. Benefits and limitations of single-wavelength and multiwavelength devices.

Benefits Limitations

Single-Wavelength

Portability: Battery-powered, can use in sites 

without available AC power. Smaller size makes the 

device easier to maneuver.

Limited search time: Battery life limits the time an 

individual can use the instrument.

Cost (individual): Individual units are typically more 

cost-effective than multiwavelength units; can 

purchase single units with most appropriate 

wavelength. 

Cost (of whole kit): Purchasing a kit containing all 

wavelengths can be more expensive than some 

multiwavelength devices.

Durability: Devices are designed for field conditions 

and can withstand harsh conditions.

Size: Smaller devices typically have smaller beams of 

light, which increases search time.

Multiwavelength

Versatility: Emits light of multiple wavelengths; can 

be used for many applications.

AC Power Dependency: Most require AC power and 

wires, which crime scenes may not have available.

Ease of use: All wavelengths are on-hand in one 

instrument, allowing easy switching between 

wavelengths.

Cost: Typically higher cost than discrete wavelength 

flashlights.

Efficiency: Typically large light beam produced; can 

cover a large search area.

Size: Large units (compared to flashlights) can lead to 

user fatigue.

When evaluating options for implementing a new ALS, decision makers must consider features of both the light 

source and the barrier filters, which are necessary to visualize the evidence illuminated by the device.

Device Considerations

Jurisdictions looking to purchase and implement a new ALS device should consider the following properties that 

influence the quality of the product, regardless of application or ALS type: 

Light Brightness: Users consistently referenced bright light as a desired characteristic in ALS devices. This quality 

improves the chance of detecting fluorescence, allowing better detection of evidence in conditions that have 

background light. Both LED and incandescent bulb-based lights can provide intense light output. In LED products, 

brightness measurements (in lumens) are typically available. However, information on the intensity of incandescent 

bulb-based ALS are not typically offered in spec sheets, so comparing intensity among bulb sources is difficult. 

Brightness can be compared, however, by testing two products at once. More information on testing products can 

be found on page 19. 

Focused Light: A high-quality ALS device produces a focused beam with uniform light throughout the beam. There 

is no “hot spot” where the center is more intense and fades out. This uniformity improves detection of evidence 

and photography results. Figure 5 shows an example of a hot spot. 
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Size: In any application, smaller and more portable units are easier to maneuver around the evidence. Lighter 

devices lead to less user fatigue. 

Battery Life: A longer battery life increases the time that investigators can use a handheld device. Interviews with

users revealed that battery life was a significant concern when working in field conditions. The representative 

sample of flashlight ALS devices in the product table are reported to have an operating time of 140–750 minutes

(~2-12 hours); however, this operating time depends on factors such as the intensity and peak wavelength of the 

light used. Interviews revealed that actual battery life is usually shorter than what is needed during an investigation. 

Maintenance: Products with long life cycles reduce the downtime of the ALS device as well as the replacement 

costs. In other words, the lifetime of the device’s bulb affects that of the entire ALS device. Replacement costs for 

bulbs can be equivalent to the cost of replacing the entire instrument. Devices with LEDs last considerably longer. 

Xenon bulbs have a typical lifespan of about 1,500 hours10 while LEDs have a lifespan of about 50,000 hours.

11

Figure 5. Demonstration of a hot spot (a) with a white light and (b) with a blue ALS visualized through orange barrier filter goggles. The light in 

the center is more intense than the surrounding light. 

Sensitivity: The smaller the range of wavelengths of light a device emits, the more sensitive the device. Sensitivity 

depends on the quality of light source used, as well as the range of wavelengths transmitted by the bandpass filter 

in incandescent light sources. Typically, manufacturers do not publish the range of wavelengths the ALS emits; 

rather, they publish the peak wavelengths for each color. 

Barrier Filter: A variety of different filter types exist, ranging in price from $10 for plastic goggles to more than 

$2,000 for specialty camera filters. Because barrier filters are necessary to view and document the evidence, 

agencies are strongly encouraged to invest in high-quality barrier filters that do not easily scratch or allow undesired 

wavelengths of light to “leak” through the filter. It is especially important that a quality camera filter is purchased 

to ultimately document the evidence that is being visualized. Potential buyers should consult their ALS 

manufacturer or distributor representative to identify the barrier filters that best fit their needs and budget.

 

10 Schneider, A., & Feussner, H. (2017). Operative (Surgical) Laparoscopy. In Biomedical Engineering in Gastrointestinal Surgery. (p 294). Academic Press. 

11 Office of Energy Efficiency & Renewable Energy, Department of Energy. LED Basics. Retrieved from https://energy.gov/eere/ssl/led-basics

(a) (b)
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While some factors, such as intensity, cannot be determined by referencing a product specifications sheet, they can 

be evaluated by comparison tests of several products. Consulting other agencies or laboratories for purchasing 

advice can also provide insight. Agencies should also base decisions on circumstances unique to their jurisdiction, 

including agency size, specific needs, and budget. 

There is no “perfect” ALS device. Many options that balance the aforementioned characteristics are available to 

support specific needs. For example, a highly sensitive device may have a lower light output due to the precision of 

its bandpass filter. An overview of specifications for common devices are featured in the Featured Product Tables

on pages 38-39. Narrowing down appropriate products requires a look at the specific applications for the ALS.

Trialing ALS Devices to Find the Best Fit 

Many manufacturers (or neighboring agencies) will allow potential buyers to borrow ALS units before 

purchasing them. This is an effective way to determine if a device fits their specific needs. Users who have 

successfully implemented new ALS devices in their jurisdictions have used these methods to test the 

instruments: 

► Using evidence samples from old cases to determine if the ALS can detect the evidence. 

► Comparing the brightness of a stain using multiple ALS products, or assessing the lowest concentration 

at which a stain can be detected by each light. 

► Testing the device at different levels of ambient light in various settings.

► Testing the battery life of the device at different power intensities (if adjustable). 

► Using the ALS to photograph samples from cases.

► Operating the device under normal conditions and observing the time required to investigate the scene 

and become fatigued from instrument use. 
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ALS Applications 

A critical factor in selecting the most appropriate ALS is 

the application for which the device will be used. While 

the technology proves to be useful in many types of 

field and laboratory applications, the most common 

disciplines in which ALS are used include the following: 

• Crime scene investigation

• Forensic biology (laboratory) 

• Latent prints (laboratory) 

• Trace evidence (laboratory)

• Medicolegal death investigation

• Forensic nursing

This section outlines roles and scenarios in crime scene 

investigation where ALS is commonly used, and 

provides factors to consider when purchasing an ALS. 

Crime Scene Investigation

ALS are commonly used to investigate crime scenes to 

identify and document evidence. The crime scene is the 

least controlled of environments in which alternate 

light sources are used. Outdoor crime scenes are 

subjected to weather conditions and lack available 

power sources. Crime scenes can range from large 

areas, such as fields, to tight spaces that limit the 

investigator’s mobility. In this application, the 

portability and size of the ALS are critical. Generally, the 

crime scene investigator looks for the widest range of 

evidence, from biological fluids—such as semen and 

saliva—to fingerprints. Once discovered, the evidence 

is collected and allocated to specialized sections in the 

crime laboratory. The most common wavelengths used 

and items searched for are presented in Table 4.

12

A compact, handheld, and battery-powered device is 

necessary to easily and effectively maneuver around a 

crime scene without causing user fatigue. The size of 

the device, however, must be balanced with the need 

for the device to generate a large beam of light. The 

smaller the beam of the light, the more time it takes for 

an investigator to cover an entire crime scene. Larger 

multiwavelength devices usually emit a larger light 

beam, which allows investigators to cover a larger 

surface area in a shorter amount of time. In situations 

where crime scenes are expansive (and an external 

battery pack or AC power is available in places such as 

a home or business), multiwavelength units are helpful. 

Because crime scenes may be in extreme conditions, 

devices should have ruggedized features such as shockproof or waterproof packaging. 

Due to the uncertainty of AC power being available 

during a crime scene investigation, ALS powered by 

batteries are the more common choice. Based on 

interviews from crime scene investigators, the battery 

life of a handheld ALS can curtail the duration of the 

investigation. To ensure proper completion of an 

investigation, many users suggest having additional 

batteries or using rechargeable batteries to 

accommodate the power needs of the individual 

device.

At a crime scene, lighting conditions are less controlled 

than those in the laboratory. Devices with a bright light 

output are helpful in identifying evidence, and can 

function well in environments where light is present. 

Most of the crime scene investigators interviewed use 

handheld units, with a majority primarily using singlewavelength, handheld lights with a blue light (~450 

nm). Blue light with orange goggles can generally 

detect the largest range of evidence; a jurisdiction with 

budgetary concerns could purchase a blue wavelength 

handheld device rather than a larger multiwavelength 

device or a set of single-wavelength flashlights.

 

12 Nichols, H., & Sanfillippo, P. (2017) Alternate Light Source Workshop: 

Course material. Tritech Forensics.
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Table 4. Common evidence detected in crime scene investigations using ALS and the respective excitation wavelengths/barrier filters 

necessary.

Evidence

Excitation Light

UV 

(260- 400 nm)

Violet 

(400-450 nm)

Blue 

(450-490 nm)

Green 

(490-560 nm)

Bitemarks/Bruises    

Hair/Fibers    

Body fluids  

Untreated blood (absorption only) 

Blood treated with fluorescein 

Bones/teeth 

Glass  

Gunshot residue 

Barrier Filters

Clear (or no filter) 

Yellow 

Orange 

Red 

Crime Scene Investigator User Profiles 

The following section provides two examples of successful ALS device implementations to illustrate benefits and 

highlight implementation considerations for crime scene applications. Key impacts and lessons learned are 

highlighted. These use profiles detail the experiences of two ALS users in crime scene applications: 

• Detective Richard Emmons, Snohomish County Sheriff’s Office

• Lieutenant Peter Cestare, Horry County Police Department 

ALS users in crime scene scenarios have addressed battery life concerns in these ways: 

► Choosing devices that are powered by conventional disposable batteries (like AA batteries), and always 

having multiple backup batteries on hand. 

► Using products that have tunable intensity—turning down the intensity extends battery life when the 

battery is getting low. 

► Purchasing devices with car chargers. 
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Detective Richard Emmons serves in the Special Investigations Unit of the Snohomish County Sheriff’s Office in 

the state of Washington. He has spent 18 years in the field and previously worked for Whatcomb County as a 

lead crime scene investigator. 

Use Profile: 

The Snohomish County Sheriff’s Office Special Investigations Unit focuses on investigating crimes against children 

and sexual assaults. Detective Emmons uses the Foster + Freeman 82S unit to detect evidence such as body fluids 

and bruising on strangulation victims. The Special Investigations Unit uses ALS exclusively in the blue wavelength 

range, but is considering the purchase of ALS in more wavelengths, such as a violet wavelength range to better 

visualize bruising. 

Detective Emmons reported that the device’s light intensity enabled illumination of evidence such as latent prints 

in low light conditions. This facilitates documentation of evidence through ALS photography because highresolution photos are easier to take with background light. Evidence fluoresces more brightly under illumination 

from the intense light of the Crime-lite 82S, which improves the quality of forensic photography. The portability and 

small size of the device also allow for easier maneuverability in crime scenes.

Detective Emmons consulted with other organizations, including 

the DNA subsection of the Washington State Patrol Crime 

Laboratory Division, to determine the features of an ALS that 

would best fit the needs of his unit. After testing several devices 

that matched these needs, he selected the Foster + Freeman 82S. 

To communicate the value of purchasing this device, he delivered 

a presentation to decision makers in his department outlining the 

advances in ALS technology and the benefits of using these 

devices in evidence collection.

Detective Emmons believes a lack of education for ALS devices remains a big challenge in the forensic community. 

From his experience in law enforcement, he understands that budget limitations may prevent procurement of 

devices or, worse, proper training for users. He noted that even the most expensive, high-quality ALS instruments 

cannot lead to successful evidence collection without proper training. Detective Emmons manages training for the 

unit and uses mocked-up example evidence to instill best practice guidelines in users. 

Detective Emmons had discussions with supervisors about exploring the concept of a centralized facility for storing 

field equipment, such as a van equipped with all necessary tools. This could allow the department to purchase one 

high-quality multiwavelength device rather than multiple single-wavelength devices. 

Device Impact:

Light intensity: Ability to detect evidence in settings 

with background light. 

Lesson Learned: 

Intense light output in ALS devices enables high-quality 

documentation of evidence with digital photography.

“Intensity is an important factor in choosing 

alternate light sources, especially for 

photography applications. Bright lights, such 

as the Crime-lite 82S, make it easy to 

document evidence.” 

— Detective Richard Emmons

Crime Scene Investigation Use: The Special Investigations Units of the Snohomish 

County Sheriff’s Office visualizes evidence in the field using Foster + Freeman 

Crime-lite® 82S lights. 
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Lieutenant Peter Cestare is the Commanding Officer of the Crime Scene Investigations Unit for the Horry 

County Police Department in South Carolina. 

Use Profile: 

The Horry County Crime Scene Investigations Unit supports patrol officers and detectives in capturing and documenting 

evidence at crime scenes. While a majority of their work lies in the field, the unit conducts preliminary screens of the 

evidence, such as searches for body fluids on a garment, in a field office before sending the evidence to the crime 

laboratory. These screens streamline investigations by reducing the amount of evidence a crime lab must process. In 

both applications, the unit uses ALS for detecting semen, saliva, urine, trace hairs and fibers, and gunshot residue. 

Different ALS devices are used in these two settings: 

1. In the field, the unit typically uses both the Lynn Peavey 

BattleLite and the Sirchie BlueMaxx, two small flashlights 

both with a single blue wavelength output. Both devices are 

small and lightweight; investigators will occasionally strap 

the portable lights to their wrists, which enables hands-free 

illumination. Lieutenant Cestare praised both the BattleLite 

and the BlueMaxx for their high-intensity light output, 

especially for their compact size. The BattleLite also 

provides a focused beam of light that allows users to 

identify potential biological fluids more reliably. 

2. The field office primarily uses the multiwavelength xenon-based SPEX Mini-CrimeScope. It is most often used as a 

stationary instrument in the facility because it requires AC power and cannot be as easily maneuvered as the 

flashlights. Because these investigators search mainly for biological fluids in ALS applications, the blue wavelength 

is favored; however, multiple wavelengths are used during preliminary evidence processing to ensure that

potential evidence fluorescing under slightly different wavelengths can be detected. Because the light from the 

multiwavelength device covers a large surface area, the device is deployed to the field in situations where large 

areas need to be covered and AC power is available. 

Lt. Cestare recognizes that training is key for quickly and effectively detecting useful evidence for a criminal 

investigation. He ensures that all ALS users in his department are trained extensively by the manufacturer before using 

the instrument. As the Commanding Officer, Lt. Cestare makes the final decision on ALS products to use within the unit. 

He did not rely on other agencies for choosing the devices because these decisions rely heavily on specific needs and 

available budget. Instead, he conducted a significant amount of research to identify suitable ALS products and tested 

them himself. He found the previously mentioned products to best suit the needs of his Crime Scene Investigations 

Unit. 

Device Impact: 

• Reliability: Intense, focused light enables more 

reliable detection of biological evidence in the field. 

• Portability: Small flashlights facilitate efficient 

searching and are easy to maneuver at a crime 

scene. 

Lessons Learned: 

• ALS devices with a large beam can cover more area 

during the search process. These tend to be large 

multiwavelength devices, but some flashlights 

produce a large beam. 

• Uniform light, in addition to intensity, increases the 

ability to detect evidence.

“I’m pleased with the Mini-CrimeScope because 

it’s versatile—you can take it out to the field and 

also use it in the laboratory.”

— Lieutenant Peter Cestare

“The BattleLite is small, compact, and gives off 

intense light for its size. This allows us to search 

more quickly during an investigation.”

—Lieutenant Peter Cestare

Crime Scene Investigation Use: The Horry County Crime Scene Investigations Unit uses 

Lynn Peavey BattleLite and Sirchie BlueMaxx lights for field work and SPEX MiniCrimeScopes for evidence analysis in their laboratory. 
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Crime Laboratory

ALS devices are used to identify evidence that requires 

further laboratory analysis. Evidence collected from a 

crime scene is brought to the crime laboratory that may 

be operated at the local or state level, or may be 

privately owned. Evidence is sent to different units 

based on forensic discipline. Forensic biology, latent 

prints, and trace evidence are three major crime 

laboratory units that commonly use ALS.

In most crime laboratory settings, multiwavelength 

devices are used because alternating current (AC) 

power is available. However, some laboratory units use 

smaller, handheld single-wavelength lights in addition 

to, or in place of, the larger units. These handhelds are 

easy to maneuver around evidence and mount on walls 

for hands-free searching. Many users believe handheld 

one-wavelength lights have comparable intensity to 

larger multiwavelength lights. Single-wavelength 

flashlights also offer versatility for units that have crime 

scene response teams.

Generally, ALS in the laboratory is utilized in low light 

conditions to make detecting evidence more effective. 

However, an intensely bright light allows laboratory 

personnel to operate in a room under brighter 

conditions. Devices with intuitive designs facilitate 

efficient use of the instrument. 

This section provides ALS implementation 

considerations specific to forensic biology and latent 

print applications. 

Forensic Biology Unit

Personnel working in the forensic biology unit use ALS 

to identify body fluids such as semen, saliva, or urine 

on collected evidence to test for the presence of DNA. 

The DNA found on the evidence is ultimately tested for 

identification purposes. Most interviewees working in 

a forensic biology unit use primarily blue light with 

orange goggles for detection of biological fluids, though 

other wavelengths can also visualize relevant evidence. 

Table 5 depicts commonly detected materials in this 

application.

Individuals working in this setting must carefully search 

for biological fluids on evidence, which could range in 

size from a small garment to a large bedsheet. Having a 

sensitive light source allows biological fluids present in 

low levels to be detected, enabling quicker processing 

of evidence. In addition, an intense light improves the 

chances of detecting fluorescence emitted by the 

sample. Because blue light can detect a wide variety of 

biological materials, a handheld single-wavelength blue 

flashlight can serve most purposes in the forensic 

biology unit.13

 

13 Nichols, H., & Sanfillippo, P. (2017) Alternate Light Source Workshop: 

Course material. Tritech Forensics.

Interviewees who use ALS in entirely pitch-black 

or low light conditions prefer devices that can be 

easily controlled in the dark. These user-friendly 

features include the ability to 

► Change wavelengths with one hand (such as 

with a thumb spinner).

► Operate the device using buttons located on 

the end of flashlights.

► Switch between wavelengths without 

turning the machine completely off. 
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Table 5. Common evidence detected in forensic biology units using ALS and the respective excitation wavelengths/barrier filters necessary.

Evidence

Excitation Light

UV 

(260-400 nm)

Violet 

(400-450 nm)

Blue 

(450-490 nm)

Semen  

Saliva  

Urine  

Untreated blood (absorption only) 

Blood treated with fluorescein 

Bones/teeth 

Barrier Filters

Clear (or no filter) 

Yellow 

Orange 

Forensic Biology User Profiles

The following section provides examples of successful implementation of ALS devices to illustrate benefits and 

highlight implementation considerations for application in the forensic biology units at different organizations. Key 

impacts and lessons learned are highlighted. These use profiles detail the experiences of two ALS users in forensic 

biology applications: 

• Dr. Christian Westring, NMS Labs

• Jenny Elwell, North Carolina State Crime Laboratory 
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Dr. Christian Westring is the Laboratory Director of Criminalistics at National Medical Servies (NMS) Labs—a 

private laboratory with extensive capabilities in forensic services, including DNA testing, body fluid 

identification, forensic chemistry, and toxicology. He oversees both the Forensic Biology and Forensic 

Chemistry units. 

Use Profile:

The Forensic Biology Unit of NMS Labs uses ALS to search for biological evidence ultimately for forensic DNA testing 

purposes. The laboratory exclusively uses the Polilight Flare Plus 2 flashlights. Because this unit of NMS Labs is 

primarily searching for biological fluids—including semen, saliva, and urine—the company purchases and uses only 

the blue flashlights that have 450 nm light. 

Dr. Westring and his team have been pleased with the performance and versatility of the Polilight Flare 2 products. 

The devices are light and can be easily maneuvered around the evidence, yet can be wall-mounted to provide handsfree illumination. Laboratory technicians can operate the instrument with one hand in a darkened room and do not 

have to worry about electrical cords impeding the analysis or posing a trip hazard. The team enjoys the lowmaintenance aspect of these LED-based lights, especially because the team does not have to replace bulbs or units 

frequently. 

NMS Labs employed a systematic validation study process to identify the 

most appropriate ALS for their needs. They tested multiple instruments 

and assessed performance-related factors, such as level of detection for 

various biological materials, brightness of stains, and level of interference 

from other materials. The Polilight outperformed similar ALS brands and 

thus was implemented in the Forensic Biology Unit. 

Dr. Westring added that the quality of the barrier filter goggles used in conjunction with the ALS affects the 

technician’s ability to detect evidence. Inexpensive goggles tend to break, scratch, or limit the visualization of 

evidence. 

Device Impact: 

• Ease of use: Using handheld flashlights instead of 

large AC power-based multiwavelength units can 

allow for more freedom to move around the 

evidence in the lab.

• Sensitivity: High-quality lights allow for better 

detection of stains, and thus biological evidence. 

• Low maintenance: LED bulbs have a long lifespan, 

and require less maintenance than incandescent 

devices. 

Lessons Learned: 

• Good quality goggles contribute to successful 

evidence detection—they must be considered in 

the budget for ALS. 

• Testing light source products is an effective way to 

identify the most appropriate device for your 

jurisdiction.

“The quality [of the Polilight Flare Plus 

2] is fantastic—we see brighter stains 

on our evidence.”

—Dr. Christian Westring

Forensic Biology Use: NMS Labs uses the Rofin Polilight® Flare Plus 2 for 

biological materials detection in the laboratory. 
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Jenny Elwell serves as a Forensic Scientist Supervisor, Technical Leader for the Serology Unit and Special Agent 

in the Forensic Biology Division for the North Carolina State Crime Laboratory. 

Use Profile: 

The Forensic Biology Division at the North Carolina State Crime Laboratory uses ALS to screen evidence for bodily 

fluids that may contain DNA. The unit previously employed a large multiwavelength device to screen evidence, but 

the light source was not intense enough to consistently detect stains containing DNA. As the technical leader and 

one of the final equipment decision makers for the division, Ms. Elwell tested ALS products and compared their

performance in visualizing evidence on samples taken from mock cases and real cases. She found that the Foster + 

Freeman 82S unit performed the best. She purchased Foster + Freeman 82S units in the blue (445 nm) and 

blue/green (475 nm) wavelengths, and these are currently the only units used in the laboratory. 

The team appreciates that the Foster + Freeman 82S handheld 

units are lightweight, battery powered and easy to maneuver in the 

laboratory. More importantly, these compact instruments are 

powerful enough to visualize evidence at low concentrations. The 

output of these LED-based devices are intense enough that, unlike 

with other ALS lights, the room does not need to be entirely dark. 

Ms. Elwell ensures that all laboratory analysts are trained on these 

instruments before using them. 

Device Impact: 

• Effectiveness: Foster + Freeman 82S units emit 

high-intensity light that can detect previously 

undetectable stains. 

• Maneuverability: Handheld ALS devices are lighter 

and less cumbersome to use than larger 

multiwavelength units. 

Lessons Learned: 

• LED-based light sources give off comparable or 

higher-intensity light than traditional 

incandescent-based sources. 

• Using evidence from past cases is an effective 

method to identify the best ALS devices to fit an 

agency’s needs. 

“The Foster + Freeman 82S product is a 

great product for what we need. It is 

lightweight and easy to handle. It may be 

small but it gets the job done and has 

made body fluid screening on bulky 

evidence much easier.” 

—Jenny Elwell

Forensic Biology Use: The North Carolina State Crime Laboratory Forensic 

Biology Division uses the Foster + Freeman Crime-lite 82S units for the 

detection of biological fluids. 
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Latent Print Unit

Laboratory technicians in latent print units use ALS to visualize fingerprints, palm prints, footprints, and other 

impressions. ALS is commonly used in conjunction with reagents to either enhance the contrast of the evidence 

with the background or cause the evidence to fluoresce. The Federal Bureau of Investigation (FBI)’s Processing 

Guide for Developing Latent Prints documents ALS as a laboratory tool for a largely diverse set of enhancement 

techniques. A wide variety of wavelengths and goggles are used in conjunction with developing agents for latent 

prints, but the most common light wavelengths used are blue, green, and yellow. Table 6 gives some examples of 

reagents, their respective excitation wavelengths, and recommended barrier filters.

Table 6. Common fluorescent fingerprint reagents used and the respective excitation wavelengths/barrier filters necessary. For a more 

extensive list of reagents and specific excitation maximums and visualization instructions, please visit the Chesapeake Bay Division 

International Association for Identification (CBDIAI) website. An asterisk (*) denotes the absorption maximum.

Excitation Light 

Processing 

Reagent

Excitation 

Wavelength; 

Absorption 

Maximum*

UV 

(260-

400 nm)

Violet 

(400-

450 nm)

Blue 

(450-

490 nm)

Green 

(490-

560 nm)

Yellow 

(560-590

nm)

Recommended 

Barrier Filter(s)

Ardrox 280-365 nm; 435-

480 nm

    Clear, Yellow

Basic Yellow 40 415-485 nm   Yellow, Orange

DFO 495-550 nm; 514*  Orange, Red

1,2-

Indanedione 515-570 nm   Orange, Red

Liqui-Drox < 400 nm (UV)  Clear (none)

M.B.D. 415-470 nm; 415–

505 nm; 450 nm*    Yellow, Orange

M.R.M. 10 430-530 nm   Orange

Nile Red 450-560 nm; 530 

nm*   Orange

R.A.M. 415-485 nm; 460 

nm*   Orange

Rhodamine 6G 495-540 nm; 525 

nm*  Orange

Safranin O ~500 nm region  Orange

TapeGlo 450 nm  Orange 

Thenoyl 

Europium

Long-wave UV (~350 

nm) 

Clear (red for 

photography)

UV-sensitive 

powders/dyes < 400 nm (UV)  Clear 
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When purchasing an ALS unit, latent print units should consider the types of reagents they use to enhance prints, 

as well as the environment in which they operate. Based on accounts of laboratory personnel with a latent print 

focus, many units use larger, incandescent bulb-based multiwavelength devices that rely on AC power. Compared 

to many applications, more wavelengths of light are employed to visualize prints and impression evidence. In latent 

print units with a crime scene response team, the large instrument usually stays in the lab when there is no available 

or reliable AC power at the scene, and teams use smaller single-wavelength flashlights, generally with a blue or 

green wavelength.

Documenting latent prints through photography is a very common practice. A practical ALS device must be sensitive 

and emit intense light so that the camera’s sensor can detect the fluorescence of fingerprints against the 

background. More information on ALS device considerations for photography applications can be found on pages

34-35.

Latent Print Unit User Profiles 

The following section provides examples of successful implementation of ALS devices to illustrate benefits and 

highlight implementation considerations for applications in latent print units. Key impacts and lessons learned are 

highlighted. These use profiles detail the experiences of two ALS users in latent print units: 

• Jennie Ayers, Idaho State Police

• Penny Dechant, Arizona Department of Public Safety
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Jennie Ayers is a Forensic Scientist and Crime Scene Coordinator for the Latent Print Section of the Idaho State 

Police. She has been in the field over 16 years, and serves as an instructor for fingerprinting, evidence 

collection, and crime scene investigation in her unit. 

Use Profile: 

The Idaho State Police Forensic Services Latent Print Section uses ALS in the central lab and field to detect latent 

prints on evidence using powders, chemicals, and other treatments. These labs use the Polilight PL400 and the SPEX 

Mini-CrimeScope, both of which are xenon bulb-based instruments. Due to their size and power requirements, the 

instruments often remain in the laboratory; however, they occasionally bring these larger instruments into the field 

when they respond to crime scenes that have electrical sources, such as homes or businesses. 

Both instruments provide multiple wavelengths of light, 

which is necessary for efficient evidence detection in the 

lab. Ms. Ayers prefers the Polilight PL400 due to its ability 

to provide an intense white light and switch between 

wavelengths without having to turn off the light. 

Device Impact: 

• Intensity: Intense light plays a large role in 

detecting evidence both at the scene and in 

the lab. 

• Efficiency: Easy switching between 

wavelengths streamlines the process of 

searching for evidence. 

Lessons Learned:

• Good-quality products have intuitive designs 

that facilitate searching for materials in dark 

environments. 

• Having multiple wavelengths available for lab 

use is more important than having multiple 

wavelengths in the field. 

• Being able to change wavelengths without 

having to turn the light off is a worthwhile 

convenience.

“Intensity of light is important in both field and lab 

settings- it’s hard to find evidence with a weak light, 

which is frustrating. The Polilight PL400 provides 

strong light for investigations, and it’s easy to switch 

between wavelengths, even in low light.” 

— Jennie Ayers

Latent Print Use: The Idaho State Police use the Polilight® PL400, SPEX 

Mini-CrimeScope, and the Polilight Flare Plus 2 Devices within their Latent 

Print Section.
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Latent Print Use: The Latent Print Unit at the Arizona Department of Public Safety uses the SPEX 

CrimeScope and Rofin Polilight Flare Plus 2. 

Penny Dechant serves as the technical lead for the Latent Print Unit at the Arizona Department of Public 

Safety. In addition to her role in casework, she is also involved in developing policies and procedures for the 

Latent Print Unit and has experience teaching latent print processing courses. 

Use Profile:

The Latent Print Unit uses two different types of ALS: the SPEX CrimeScope CS-16-500W and the Polilight Flare Plus 

2 flashlight. Because the CrimeScope is a large multiwavelength unit that requires outlet power, it typically stays in 

an examination room. While technicians use all wavelengths in the CrimeScope device, they typically focus on 

wavelengths that enhance visualization of evidence treated with certain processing techniques. For example, the 

team typically uses light at a blue wavelength for processing with superglue and fluorescent dye stain. Ms. Dechant 

reports that the CrimeScope provides consistently high-quality lighting for documenting processed evidence with 

photography. 

In addition to the CrimeScope, the unit purchased Polilight Flare Plus 

2 flashlights to provide more ALS options for their examiners beyond 

the multiwavelength device. The Latent Print Unit decided to 

purchase the Polilight Flare Plus 2 flashlights after attending the 

International Association for Identification (IAI)’s International 

Forensic Educational Conference and testing the products there. The 

examiners in Ms. Dechant’s unit were pleased with the portability of 

the devices, which allows her team to use the ALS at their desks rather 

than the examination room. The handheld Polilight Flare Plus 2 is easy 

to maneuver around evidence, which allows the team to work more 

efficiently. Ms. Dechant noted that examiners use these devices to 

photograph the processed evidence, in addition to the CrimeScope. 

Device Impact: 

Efficiency: Having portable ALS devices available 

allows for efficient evidence processing. 

Lessons Learned:

• The wavelengths necessary for latent print 

detection usually depend on the developing 

agents they use to process the prints. 

• Portability of ALS device provides value to 

laboratory applications as well as field 

applications. 

“The CrimeScope lighting is consistent 

and reliable. It has the capability to be 

used in the field but we haven't had the 

need as of yet. The [Flare Plus 2’s] 

portability is a big sell for our examiners 

because they can do searching from 

their desk instead of going to the 

[examination] room.” 

—Penny Dechant
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Trace Evidence Unit 

Trace evidence units in crime laboratories search for and test materials—such as glass, fibers, and residues—both 

at the crime scene and on evidence collected at the crime scene. ALS are used to better visualize this evidence, 

which is tested and identified through analytical laboratory techniques. Table 7 shows common wavelengths used 

to identify trace evidence.

Table 7. Common trace evidence types detectable and the respective excitation wavelengths/barrier filters necessary.

Excitation Light

Evidence

UV 

(260-400 nm)

Violet 

(400-450 nm)

Blue 

(450-490 nm)

Green 

(490-560 nm)

Hair/Fibers    

Gunshot residue 

Metallic Residue 

Glass  

Barrier Filters

Clear (or no filter) 

Yellow 

Orange 

Red 

Like the latent print unit, trace evidence uses a wider variety of light wavelengths at the scene and in the laboratory. 

Flashlight sets with multiple wavelengths or multiwavelength units work well for trace evidence analysts. While the 

evidence analyzed in the trace evidence unit differs from that analyzed in the forensic biology and latent print units, 

ALS-specific protocols are very similar. For this reason, trace evidence examiners were not explicitly profiled in this 

report. 
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Other Applications

ALS are useful in applications beyond crime scene and 

laboratory settings, such as forensic nursing and 

medicolegal death investigation. 

Medicolegal Death Investigation

Medical examiners investigate homicides and 

suspicious deaths both in context at the crime scene 

and in the morgue. By examining the body of a 

deceased victim, medical examiners provide insight to 

investigators about the cause and manner of death and 

can assist in identifying and collecting evidence for 

further analysis. Medical examiners may use ALS in a 

darkened examination room to search for biological 

evidence on the body—such as semen and saliva—as 

well as patterned and unusual injuries. Blue light or UV 

is usually employed for detecting biological materials; 

for bruising and patterned injuries, multiple 

wavelengths and barrier filters can detect ecchymosis, 

depending on how deep the injury penetrates the skin. 

Ecchymosis is defined as discoloration of the skin due 

to ruptured blood vessels, and it results in blood 

leakage into subcutaneous tissue. Multiwavelength ALS 

devices, therefore, are very useful in these settings. 

Because the room is darkened, devices with intuitive 

features (refer to page 24) are valuable for ease of use. 

Evidence collected from the body is photographed in 

this context; therefore, valuable ALS sources for this 

application emit intense light to detect evidence at low 

concentration levels.

Forensic Nursing 

Forensic nurses treat victims who have survived violent 

crimes, often domestic violence and sexual assault, in a 

clinical setting. The nurse can alert law enforcement to 

potential evidence, such as semen or saliva, on the 

victim for collection and processing. Additionally, 

forensic nurses can detect pattern injuries on the 

victim, such as ligature marks from victim-reported 

strangulation. Similar to medical examiners, forensic 

nurses use blue or UV to search for biological fluids and 

use a wide variety of wavelengths and barrier filters to 

search for bruising. High-intensity light is critical to 

penetrating layers of skin to visualize bruising, and 

multiwavelength units are preferred. Photography of 

the noted injuries is also very important. Read more 

about the importance of ALS photography on pages 34-

35.

Generally, ALS is used as a court-admissible screening tool to identify evidence that will ultimately be tested in 

a laboratory. For example, suspected body fluids on a garment detected by ALS will be tested for the presence 

of DNA. In forensic nursing, however, ALS does not act as solely a screening tool to detect bruising on crime 

victims. Forensic nurses must speculate the presence of bruises through ALS imaging and, unlike medical 

examiners, are unable to confirm the presence of bruising in an autopsy.

The use of ALS as a method to diagnose sub-clinical bruising has remained a controversial topic. Multiple 

publications have argued for and against the admissibility of bruising detected by ALS. In 2010, a Frye-Reed 

hearing was conducted in the state of Maryland; the judge ruled that use of ALS in forensic nursing was 

acceptable and permitted inclusion of testimony based on use of ALS devices. 

Publications and news articles regarding the use of ALS in forensic nursing include the following: 

Baltimore Sun: New Technology Helps Convict Domestic Abuse Suspect

Journal of Forensic Sciences: Is Fluorescence Under an Alternate Light Source Sufficient to Accurately Diagnose 

Subclinical Bruising? 

Journal of Forensic Nursing: Use of an Alternative Light Source to Assess Strangulation Victims
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34

ALS Photography

Photography is an essential tool for documenting the 

processing of a crime scene. ALS photography is a type 

of forensic photography that visualizes and documents 

evidence—such as fingerprints and biological 

materials—that is not always visible to the naked eye.

In most cases, ALS photography takes place in a 

controlled setting, such as a laboratory or a windowless 

examination room in a morgue. The room is darkened 

to enhance the effect of the light source on the 

evidence. However, ALS photography may also occur at 

crime or death scenes where the user has less control 

over the light conditions. 

ALS are not only used to detect evidence, but are also 

used to document it for court purposes through 

photography. Therefore, basic photography skills are a 

critical prerequisite for effectively documenting 

evidence through ALS photography. The user must fully 

understand how to manually operate camera settings 

and cannot rely solely on the automatic setting. If the 

photographs taken at the scene or in the lab do not 

accurately reflect the visualized fluorescence, then the 

importance of the evidence cannot be effectively 

communicated to the jury. 

Figure 6 provides examples of common mistakes made 

when searching for and photographing evidence with 

ALS. Figure 6 also demonstrates the importance of 

using the correct barrier filter and camera settings 

when photographing evidence. The wavelength, 

barrier filter, and camera settings used all play an 

integral part in obtaining a photograph that accurately 

represents the evidence that has been detected.

Key ALS features that are especially important for 

photography include the following: 

► Light intensity and device sensitivity, so 

evidence fluoresces brightly against the 

background. 

► Large light beam that uniformly illuminates the 

evidence and minimizes incidence of false 

positives. 

► Effective heat dissipation so that evidence 

illuminated by an ALS is not warped, melted, or 

destroyed in the photography process. 
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Figure 6. Semen stain illuminated under various lighting conditions using different camera settings. (a) white light; stain is hard to visualize, 

and there is little contrast between the stain and the background (b) blue (475 nm) light with orange barrier filter; proper camera settings; 

well-defined stain (c) blue light with no barrier filter; blue light overpowers fluorescence (d) blue light with incorrect (red) filter; stain not 

clearly defined (e) blue light with yellow barrier filter; some contrast, but not optimal (f) green light (515 nm) with orange barrier filter; 

incorrect wavelength of light used, so no visible fluorescence (g) blue light with orange barrier filter; built-in camera flash used (h) blue light 

with orange barrier filter; no tripod used; blurry. Photo credit: Heidi Nichols, Miami-Dade County Medical Examiner Department.

(g)

(a) (b) (c)

(d) (e) (f)

(h)
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ALS Device Education 

Educating both purchasers and users on the capabilities 

and limitations of alternate light sources is critical to 

successful procurement and implementation of these 

devices. The following section illustrates the 

importance of educating both buyers and users of the 

technology.

Education for Decision Makers and Purchasers

User interviews have indicated that in many agencies 

and laboratories, the users of ALS devices often do not 

have the authority to purchase them. It is therefore 

critical to communicate the value of this technology to 

decision makers and purchasers. These stakeholders 

need to understand the technology behind the ALS 

devices as well as clear capabilities and limitations of 

these instruments. 

In addition to educating decision makers about the 

benefits, capabilities, and limitations of ALS devices, 

agencies must convey the necessity of training users on 

the device. The following section justifies the 

importance of training in ALS implementation. 

Training for Users

The capabilities of ALS, regardless of quality and price, 

depend heavily on the user’s ability to operate the 

device correctly. There is no universal standard 

operating procedure or training protocol for these 

devices; agencies must train their ALS users for their 

specific needs. Some jurisdictions bring in trainers from 

manufacturers, distributors, or training companies,

while other jurisdictions may develop their own 

curriculum or do on-the-job training. Training users on 

the technology requires both time and financial 

investment, and its value should be communicated to 

decision makers. Benefits of training include the 

following: 

More reliable detection of evidence: Users who fully 

understand how to operate ALS devices and have 

practiced using them 

with real samples are 

more likely to detect 

evidence in the crime 

scene or laboratory. 

The more experience 

users have with the 

devices, the more likely 

they are to successfully 

use them during 

casework (Figure 6).

Quicker processing time: Trained users develop a keen 

eye for fluorescent materials over time. Those 

individuals who developed a solid training foundation 

are more confident to correctly handle equipment and 

conclude that no relevant evidence is present. Because 

trained individuals know what to look for, they can 

identify and collect evidence more quickly. 

Additionally, field and laboratory technicians may

submit fewer “false positive” samples to the 

laboratory, which speeds up the processing time. 

Better documentation: Field and laboratory users who 

detect evidence using ALS must be able to document 

the information so that it may be used in the 

investigation. ALS photography requires not only 

knowledge on how to effectively operate the ALS 

device, but how to capture these results with a digital 

camera. Users who have refined these skill sets in 

Detective Emmons, who serves in the Special 

Investigations Unit of the Snohomish County 

Sheriff’s Office, communicates the value of ALS 

devices to his department’s decision makers by 

giving detailed presentations on the technology 

and circulating literature on selected products. 

These presentations provide decision makers with 

the necessary background and justification for 

purchasing a specific device. 

“We assume that people 

who buy the high-end 

lights know how to use 

them, but that’s not the 

case.” 

—Detective Emmons, 

Snohomish County 

Sheriff’s Office

“99% of the time, people don’t read the manual, and 

don’t know how to use the instrument. Most of the 

problems we encounter come from user error. You 

need to take the time to read the instructions that 

come with the equipment and practice the 

applications so there is no confusion or questions in 

the field. Practice builds proficiency!” 

—Lieutenant Peter Cestare, 

Horry County Police Department
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training can more effectively document the evidence 

they can visualize. 

More confidence in court: Crime scene investigators 

and laboratory technicians who understand the 

technology, as well as the capabilities and limitations of 

ALS, are better able to confidently testify in court. 

Interviews with ALS users at a training course revealed 

that many investigators did not feel comfortable 

defending the subject matter in court without 

undergoing ALS training. Training provides experts with 

the background and vocabulary to effectively relay 

information to jurors, lawyers, and judges.

Training opportunities, especially those that foster the 

collaboration between multiple agencies, can promote 

the dissemination of proper techniques in the field. 

Attending conferences such as the International 

Association for Identification (IAI) can help agencies to 

find training opportunities to fit their needs.

Featured ALS Product Landscape

This section provides a more detailed product landscape for selected ALS devices consistently referenced in user 

interviews. Tables 8 and 9 provide useful information for purchasing both single-wavelength and multiwavelength 

devices. Note that these tables only include devices that were mentioned in the user profiles.
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Selected Single-Wavelength ALS Devices 

Table 8. This table provides a detailed product landscape for selected single-wavelength ALS devices.

Manufacturer Foster + Freeman Lynn Peavey Rofin Forensic

Website http://www.fosterfreeman.com/ https://www.lynnpeavey.com/ http://www.rofinforensic.com.au/

Instrument CrimeLite 82S Battle-Lite Polilight Flare Plus2

Cost

$: $0-$500

$$: $500-$2,500

$$$: $2,500-$10,000

$$$$: $10,000-$15,000

$$$$$: $15,000+

Full set: $$$$$

Per flashlight: $$$

Full set: $

Per flashlight: $

Full set: $$$$

Per flashlight: $$

Light 

Source

Bulb LED LED LED

Power/Intensity 5280 lumens 700 mW (high on 455nm) 3300 lumens (white)

Flashlight Type Discrete Switchable heads Discrete

Wavelengths (nm)

White x x x

Red 640 - 620

Orange 590 - -

Yellow - - -

Green 520 505 530, 545

Blue-green 472 - 505

Blue 445 455 450

Violet 410 - 415

UV 365 395 365

User Experience

Power Source Battery Battery Battery

Battery Type Rechargeable Lithium Ion Lithium Ion Rechargeable Lithium Ion

User replaceable? Yes Yes No

Battery life (at 100%) up to 750 minutes > 2 hours Up to 300 minutes

Weight (lbs.)

Including batteries if 

applicable

1.2 0.3 (including batteries) 1.5

Ruggedization Yes Dust, shock, and weather 

resistant

Submersible up to 100 m., salt 

water resistant

Available as a set Yes. Kits of 1 to 9 lights Yes Yes

Available Individually Yes Yes Yes

Warranty 1 year 1 year 1 year

Training

Availability of Training Yes Yes No

Additional Charge Yes No N/A
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* - denotes longpass filter

† 

- denotes shortpass filter

Selected ALS Multiwavelength Units

Table 9. This table provides a detailed product landscape for selected multiwavelength ALS devices. 

Manufacturer Horiba Scientific SPEX Forensics Rofin Forensic

Website https://spexforensics.com/ http://www.rofinforensic.com.au/

Instrument

(Model #)

CrimeScope Mini-CrimeScope Polilight PL400

(CS-16-500W-15F) (MCS400-8F)

(MCS400-16F) PL400 Forensic PL400 Forensic 

Plus

Cost

$: $0-$500

$$: $500-$2,500

$$$: $2,500-$10,000

$$$$: $10,000-$15,000

$$$$$: $15,000+

$$$ $$ $$$ $$$$

Light 

Source

Bulb Xenon Arc Metal Halide Metal Halide

Power/Intensity 500W 400W 400W

Wavelengths (nm)

White x x x x x

Red 635, 670 - 630 - 620, 650

Orange 600 - 600 -

560, LP560*, 

570, 590

Yellow SP575†-

SP575†, 

575

- -

Green SP540†

, 515, 535, 

555

SP540†, 

515, 535, 

555

SP540†, 

515, 535, 

555

530 515, 530, 550

Blue-green 495 - 495 505 505

Blue 445, 455, 475 455 445, 455, 

475

450, LP350*, 

490

430, 450, 

LP350*,470, 

480, 490 

Violet 415 415 415 415 415

UV 365 365 365, 390 350 350

User 

Experience

Power Source AC Power AC Power AC Power

Weight (lbs.)

Including batteries if 

applicable

- - 14.3

Warranty 1 year 1 year 1 year

Training

Availability of Training Yes Yes No

Additional Charge N/A - N/A
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Manufacturer Profiles

While the ALS market has many players, these four manufacturers were consistently referenced during user 

interviews: 

Foster + Freeman

Foster + Freeman was established in 1978 and has developed numerous products for forensic examination, with 

applications including questioned documents, fingerprint examination, and trace evidence analysis. One of the 

company’s goals is to create products with end users in mind, ensuring that products are rugged and easy to use.

Foster + Freeman offers handheld and benchtop alternate light sources, both of which use LED technology. The 

Crime-lite 82S is their flagship handheld ALS device—this flashlight has 16 LEDs chosen for brightness and 

wavelength accuracy. ML2, a benchtop ALS product, features a rotating arm and an attachable filter so that the user 

is not required to wear goggles. Foster + Freeman offers training courses and workshops for all of their products.

Unique Product Features

• These LED-based products are designed to give the same light output even when the battery decays or 

the light heats up. This ensures that the intensity of the light does not change, resulting in consistent 

search results.

• The 82L floor lamp is an ALS device that brightly illuminates large floor or wall sections with white or UV 

source. 

• The Crime-lite Eye is a pocket-sized LED device that helps crime scene examiners achieve dark adaptation 

before using an alternate light source. 

HORIBA Scientific SPEX Forensics

HORIBA was established in 1953 as a company that manufacturers a large range of analytical devices for many 

markets—including automotive, medical, and pharmaceutical applications. HORIBA Scientific was created to better 

meet customers’ needs in the scientific markets of fluorescence, forensics, spectroscopy, particle characterization, 

and more. 

The HORIBA Scientific SPEX Forensics Division was established in 1993 as a forensic light source manufacturer. 

Today, the SPEX division sells more than just FLS, including fingerprint image enhancement systems, automated 

fingerprint identification systems (AFIS), and the Reflective Ultra Violet Imaging System (RUVIS). Some of the FLS 

manufactured by SPEX Forensics include the CrimeScope, the HandScope® LED, the HandScope Xenon, and the 

FOCUS flashlight.

The SPEX division of HORIBA Scientific provides forensic training programs for law enforcement, crime scene 

investigators, and other personnel who use forensic light sources. SPEX Forensics will train individuals how to use 

SPEX products as well as other ALS that are already implemented within the agency.

Unique Product Features

• SPEX ensures that their products do not produce hotspots—all light is distributed evenly. Hotspots can 

reduce quality of the fluorescence emission that is seen. 

• Typically, multiwavelength units are powered by incandescent bulbs. However, SPEX offers a 

multiwavelength LED device—the HandScope LED—which emits light at five different wavelengths. 
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• The SPEX warranty covers both the device and the battery. This is unique because most companies do not 

provide battery warranties.

Lynn Peavey Company

Lynn Peavey Company—based in Lenexa, Kansas—has been in the forensic science business for 65 years. In addition 

to supplying ALS, this company provides latent fingerprint developing reagents, evidence seals, laboratory supplies, 

and more. The BattleLite is Lynn Peavey’s portable, LED-powered 455-nm blue light that is built for military and law 

enforcement applications. Lynn Peavey offers training for their ALS products. 

Unique Product Feature

• The BattleLite is built to be military-grade and is resistant to dust, shock, and weather.

Rofin Forensic

Rofin Australia Pty Ltd was established in 1978 as a marketing company for scientific instruments and expanded 

into the forensic science business in 1988. Rofin’s forensic instrument product line is used in more than 3,000 

locations in 77 countries by leading agencies including the FBI, Central Bureau of Investigation (CBI) and Scotland 

Yard. Rofin Forensic offers both multi wavelength and single wavelength ALS devices, which use either arc lamps or 

LED-based bulbs. Their Polilight Flare Plus 2 is a battery-operated, portable, LED forensic light source (FLS) that was 

designed for use at a crime scene. Their Polilight PL500 is their flagship forensic light source with a 500-watt xenon

arc lamp. Recently a newer version, the PL-550XL was released. Both are housed in an aluminum case for shock 

protection and easy transportation. Rofin does not offer formal training, but training on their products is offered 

through their local distributors.

Unique Product Features

• The Polilight Flare Plus 2 flashlights have an effective cooling system that does not require a fan, which is 

more reliable and prevents disruption of evidence at the scene or laboratory. 

• A high performance bandpass filter is incorporated into the LED-based Flare Plus 2 flashlights, improving 

the sensitivity of the device. The units are waterproof and submersible.

• Flashlight intensity is adjustable, which facilitates searches and evidence documentation by photography.

• The PL550XL xenon system offers higher output through a unique lamp boost mode feature and fan speed 

controller. Output power is user controlled.

• Wavelength fine-tuning of the 12 to 20 Bands provides many thousands of output color options

• The PL500 and PL550XL offer various length light guides and mounting points for use in the lab and at 

crime scenes.

• The PL500 and PL550XL are available with full featured remote controls for operation up to 5 meters away 

from the unit.
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Summary

Alternate light sources are an integral part of crime and death scene processing and evidence analysis, and agencies 

looking to replace their outdated or broken instruments must navigate a crowded market of over 15 manufacturers 

and 50 products. The goal of this landscape study is to enable laboratory directors, crime scene investigation units, 

and other decision makers to make better informed decisions when purchasing ALS devices. The information 

contained herein is derived from current literature and interviews with technology experts, developers, and users 

in a wide variety of applications. This document provides the reader with a basic understanding of alternate light 

source technology, implementation considerations, user experiences with the technology, and a comparison of 

selected ALS devices. 

Alternate light sources are used in both field and laboratory applications within forensic science. While agencies 

must consider the end applications of these devices when purchasing these products, general implementation 

considerations include the following: 

Type of ALS Device: ALS devices are generally offered as large, multiwavelength units with AC power or handheld, 

battery-operated single-wavelength flashlights. The multiwavelength units tend to stay in the laboratory, while 

single-wavelength units are consistently being used in both field and laboratory applications. User interviews 

indicate both types of devices have comparable light intensity and sensitivity in detecting evidence. 

Key Features of ALS Devices: Device purchasers should consider quality drivers of the product that include the 

following: 

• Light brightness

• Focused light

• Size

• Battery life

• Maintenance

• Sensitivity

Barrier Filters: Purchasers must invest in quality barrier filters with a documented cutoff wavelength to facilitate 

visualization of evidence illuminated by ALS. 

Device Education: It is critical that users are properly trained in both visualizing and documenting evidence using 

ALS, and that decision makers understand the capabilities and limitations of these devices. 

Cost: Agencies must consider the cost of the ALS device, barrier filters, maintenance, and training when determining 

the best ALS options for their budget. 

While alternate light source technology has been used in forensic science for multiple decades, today’s products 

incorporate advanced technologies—such as LEDs, compact packaging, and precise bandpass filters—that improve 

the user experience and may lead to better detection outcomes. The FTCoE hopes that the information provided in 

this report will help users and purchasers to make an informed decision regarding the procurement of ALS devices 

for their units so that ALS can help identify and document evidence, ultimately supporting law enforcement efforts. 
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Image Credits

Cover Photo – fired/shutterstock.com 

Figure 3 – Heidi Nichols, Miami-Dade County Medical Examiner Department

Figure 5 – 5(a) RTI staff, 5(b) Heidi Nichols, Miami-Dade County Medical Examiner Department

Figure 6 – Heidi Nichols, Miami-Dade County Medical Examiner Department

All device graphics in Tables 8 and 9 are used with permission from the respective manufacturers. All agency logos 

are used with permission from the respective agency.
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The Forensic Technology Center of Excellence 

RTI International (RTI) and its academic and community based-consortium of partnerships, including its Forensic 

Science Education Programs Accreditation Commission partners, work to meet all tasks and objectives put forward 

under the National Institute of Justice (NIJ) Forensic Technology Center of Excellence (FTCoE) Cooperative 

Agreement (award number 2016-MU-BX-K110). These efforts include determining technology needs; developing 

technology program plans to address those needs; developing solutions; demonstrating, testing, evaluating, and 

adopting potential solutions into practice; developing and updating technology guidelines; and building capacity 

and conducting outreach. The FTCoE is led by RTI, a global research institute dedicated to improving the human 

condition by turning knowledge into practice. The FTCoE builds on RTI’s expertise in forensic science, innovation, 

technology application, economics, data analytics, statistics, program evaluation, public health and information 

science.

Disclaimer

The FTCoE, led by RTI International, is supported through a Cooperative Agreement from the NIJ (2016-MU-BXK110), Office of Justice Programs, U.S. Department of Justice. Neither the U.S. Department of Justice nor any of 

its components operate, control, are responsible for, or necessarily endorse, this landscape study.

Information provided herein is intended to be objective and is based on data collected during primary and 

secondary research efforts available at the time this report was written. Any perceived value judgments may 

be based on the merits of device features and developer services as they apply to and benefit the law 

enforcement and forensic communities. The information provided herein is intended to provide a snapshot of 

current alternate light source developers and a high-level summary of available devices; it is not intended as an 

exhaustive product summary. Features or capabilities of additional instruments or developers identified outside 

of this landscape may be compared with these instrument features and service offerings to aid in the 

information-gathering or decision-making processes. Experts, stakeholders, and practitioners offered insight 

related to the use of alternate light sources for law enforcement agencies.

January 2018