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Infrared Toolmark Imaging 

Forensic Applications

Francine Prokoski

President

Infrared Identification Incorporated

• Common Origin of Fired Ammunition Components

• Authentic or Counterfeit Electronic Components
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IR Film 

 IR Viewers

 

 Analog Cameras

 Radiometric

Digital Cameras

 

 

60 Year Development of Infrared Imaging

Calibrated

3D/IR Systems

inches

 mm

 

 microns
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Traditional Infrared Imaging

- Surveillance, Night Driving

- QC, Process Control, Fire Safety, 

Health Monitoring

- Plume Analysis,Trace Evidence, 

Camouflage Detection

USES:

 Nonilluminated Vision

Temperature Measurement

Spectral Analysis

TECHNICAL ISSUES LIMITING USE:

 Small Array Size

Shallow Depth of Focus

Strong Influence of Emissivity on Temperature Measurement

Motion Blur with Uncooled Detectors
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NonTraditional Infrared Imaging

- Forensic Toolmark Detection & ID

- Industrial NonContact Inspection for Surface 

Defect at site of Thermal Anomaly

- Medical Assessment of Wound, Incipient 

Infection, Adverse Reaction to Vaccination

USES:

 Emissivity Mapping

IMPORTANCE OF TECHNICAL ISSUES:

 Small Array Size - High Magnification Optics, Small Local Features

 Shallow Depth of Focus – CNC-Controlled Range Gated Sequences

 Strong Influence of Emissivity – Increases Toolmark Detection

 Motion Blur with Uncooled Detectors – Lock-on Toolmark Details
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Emissivity Effect: Actual vs. Apparent Temperature

 Variations in Materials

 Different Surface Processing

 

Must Know  to Calculate Actual Temperature from Apparent Temp

 is a Measure of Emission Efficiency

 Function of: Distance, Atmosphere, Optics, Spectral Band, Surface

 Texture, Surface Geometry Relative to Camera, Material 

 Composition, Color, Temperature, etc.

Plastic, Glass, and Metal Surfaces

All at the Same Room Temperature 

Appear to Have Highly Detailed

Temperature Variations in IR Images

Sample Values: Polished Aluminum = 0.05 (inefficient) 

 Human Skin = 0.98 (efficient)
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Variations in User’s Force, Angle, Path, and Motion Affect Mark

Analysis Must Link Mark to Tool or Mark to Mark

3D Nature of Toolmarks Complicates VL Imaging

Manual Toolmarks

Two Different Users Make Impression + Striae Marks with Screwdriver

 VL Images IR Images with CutLine CutLine Waveform as BarCode

Ruler in

1/36 inch

Toolscrape018 

Toolscrape218
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First Swath with Tool #18

Second Swath with Tool #18

Depth Profiles – Not Aligned

FFT of Depth Profiles – Not Scale Normalized 

Frequency Domain Comparison of Toolmarks

Different Person, Same Tool

New Slide
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Identification of Manual IR Toolmarks

 Magnification is Required to View/Extract Toolmark Features

 Traditional Approach uses Visible Light Imaging

 With Ring or Oblique Light Source

 Light Variations and Artifacts Affect Reliability 

 IR imaging Eliminates Lighting Adjustments and Anomalies 

 Greater Image Reliability Allows For Higher Accuracy 

 No Illumination Tuning Allows Automated Capture & Comparison

Automated IR Imaging and Matching 

of 400 Screwdriver Marks 

Ranked 87% of Siblings in #1 Place

 vs. 16% for VL Imaging
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Automated Toolmark Production

Semiautomatic Hand Gun is Example

Of a Manufacturing Process Involving

Multiple Actions Leaving Toolmarks
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Primer Area of Magnum .44 cal – casing #18

VL image of breechface 

Impression

IR Image of breechface 

Impression

Automated Toolmarks
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VL Image of firing pin 

impression

IR focused on firing pin

detail

Firing Pin Details of Magnum .44 cal – caseing #18

Automated Toolmarks
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Glock VL and IR Images

Whole FOV

Primers

Characteristic Primer Shearing Marks from Firing Pin Aperture

Details are More Clear in the IR Images 
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Technical Issues in Toolmark Analysis

DEPTH OF FOCUS: Very Shallow

CNC Controls Focus Distance to Provide Precise Range Gating

Synchronization with IR Camera Encodes Depth into Each Frame’s Header

3D Rendition of Toolmark Impressions and Striations Can be Formed from 2D Slices

Selected Frames
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IR Identification of Glock Casings

Shape of FP Aperture

Relative Position FP Indent

Shearing Striae Left (Bottom)

Shearing Striae Right (Top)

Breechface Impressions

Within Primer

Outside Primer

FP Indent Details

Anomalous Marks

Within Primer

Outside Primer

Automatic Generation of 1D and 2D BarCodes
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 Axes Reference Inner and Outer Primer Edge Circles

 Center is Center of Rotation

 FP Aperture Rectangle is Horizontal with FP Drag to Right

CutLines 7 8 and 9 Characterize Shearing Marks

CutLines 10 and 11 Locate Breach Marks Outside and FP Indent Within Rectangle

MEASUREMENTS Compared to Standard:

Circularity of CC and primer

Aperture Size & Position

FP Indent Location

CutLine Waveforms:

 Breach & Shearing

IR Quality Control Monitoring of Glock Firearm

Define Standard Orientation; Reference Landmarks
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Casing Identification by Primer Sheering Code

CC388 f075 CC304 f053

Greyscale Variations Ignored

Striae Locations are Compared

Sibling Glock Casings

Compare 1D BarCodes from Vertical CutLines through Primer Sheering

Strongest 1D Match Test

96% Siblings Ranked #1
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Concentric Rings about FP Center

Compensates for Imprecise Rotation Correction

Better Fit to Primer Shearing Curvature

Set of Concentric CutLines Produces 2D BarCode

Linear Vertical CutLines

Equal-spaced Shifted through FP Center

Sensitive to Rotation Correction

Set of CutLine Waveforms Produces 2D BarCode

CutLine Patterns Selected by Part Design

Use of Multiple CutLines Improves Matching

Chose CutLine Density to Cover Production
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Identification by 2D Firing Pin Code

Sibling Casings

FP IR Image Frames

@ Specified Focus

2D Barcode Format

Align & Difference

CC 085 FP and Barcode CC 084 FP and Barcode

 94% Correlation

Within 1 grey level
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FP CC091 Re-Scans

Barcode Correlation 99.6%

FP CC091 CC085 Non-Siblings

Barcode Correlation 24.5%

FP CC090 CC091 Siblings

Barcode Correlation 98.5%

Reliability of Self-Generated Toolmark Codes

Self-Generated IR Barcodes

Provide Accurate Identification

Of Toolmarks
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tan is Target silver is Sibling

TOP EIGHT MATCHES FOR TARGET 

WITH POSITION OF SIBLINGS FROM OBSERVATION

Rank 1 2 3 4 5 6 7 8

Template 1072 1159 1164 1092 1160 1079 617 629 611

FeatureCount 10518 10549 10194 10436 9928 10815 10507 10651 10293

MatchCount 10518 3838 3695 3740 3345 3052 2791 2819 2664

MatchValue 1.000 0.357 0.356 0.352 0.330 0.276 0.260 0.259 0.253

Evaluating Match Value Algorithm

Match Value Combining FP and Sheering Comparison Results Against 600 CCs

Match Value Ranked All Siblings

In Top Positions for 600 CCs
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Glock Toolmarks on Primer

VL with oblique visible light illumination 

 NIR with NIR illumination

 IR with no illumination

Passive IR imaging generates more highly detailed Toolmarks

With greater repeatability than visible light or near IR imaging
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CC #15 fired from Glock 9mm 

Imaged with a 500 frame IR sequence:

 

Frame 272 has deepest firing pin impression features in focus

Frame 315 has primer sheering marks in focus

Fusion of the two frames is used to search reference database for a match

 Firearm/Ammunition combinations that produce breechface impressions

 may use fusion of three frames for database searching

 Firing pin impressions are not fused with other feature frames in the

 case of Firearms whose firing pin position & orientation are not fixed 
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FPI, Primer Sheering, and Fused Frames from

 Sibling Casings fired from the same Glock

Glock A Cartridge Case #15

Glock A Cartridge Case #14

Comparison of Thermal IR Toolmark Images of

Firing Pin Impressions and Primer Shearing Marks on

Two Cartridge Cases fired from the same Glock
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TOP MATCHES TO CC1006 FIND ITS 1 SIBLING IN RANK #1

WITH MATCH VALUE 0.315 tan is Target silver is Sibling

TOP EIGHT MATCHES FOR TARGET 

WITH POSITION OF SIBLINGS FROM OBSERVATION

Rank 1 2 3 4 5 6 7 8

Template 1006 1063 1092 260 254 213 266 243 278

FeatureCount 9982 10937 10436 11699 11629 11757 10895 11370 11195

MatchCount 9982 3550 2699 2677 2669 2634 2561 2538 2519

MatchValue 1.000 0.315 0.253 0.217 0.218 0.212 0.228 0.214 0.216

tan is Target silver is Sibling

TOP EIGHT MATCHES FOR TARGET 

WITH POSITION OF SIBLINGS FROM OBSERVATION

Rank 1 2 3 4 5 6 7 8

Template 1006 1063 1092 260 254 213 266 243 278

FeatureCount 9982 10937 10436 11699 11629 11757 10895 11370 11195

MatchCount 9982 3550 2699 2677 2669 2634 2561 2538 2519

MatchValue 1.000 0.315 0.253 0.217 0.218 0.212 0.228 0.214 0.216

IR2IR Automated Comparisons of 262 Glock CC

TOP MATCHES TO CC1006 INCLUDE ITS 1 SIBLING IN RANK #1 

WITH MATCH VALUE 0.315
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SUGGESTS MATCH THRESHOLD ABOVE 0.253

tan is Target silver is Sibling

TOP EIGHT MATCHES FOR TARGET 

WITH POSITION OF SIBLINGS FROM OBSERVATION

Rank 1 2 3 4 5 6 7 8

Template 1159 1092 1072 1160 1089 1102 255 1100 256

FeatureCount 10549 10436 10518 9928 9959 9549 10597 9886 10786

MatchCount 10549 4532 3862 2636 2580 2458 2704 2520 2740

MatchValue 1.000 0.427 0.360 0.259 0.253 0.250 0.250 0.249 0.248

TOP MATCHES TO CC1159 INCLUDE ITS 3 SIBLINGS IN RANK #1,2,3

WITH MATCH VALUES FROM 0.259 to 0.427
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TOP MATCHES TO CC1016 CORRECTLY FIND NO SIBLINGS 

HIGHEST MATCH VALUE 0.232 tan is Target silver is Sibling

TOP EIGHT MATCHES FOR TARGET 

WITH POSITION OF SIBLINGS FROM OBSERVATION

Rank 1 2 3 4 5 6 7 8

Template 1016 632 234 266 260 1079 214 605 638

FeatureCount 10225 11476 11474 10895 11699 10815 12154 10688 10803

MatchCount 10225 2769 2697 2612 2586 2576 2578 2560 2532

MatchValue 1.000 0.232 0.226 0.233 0.211 0.232 0.199 0.234 0.228

TOP MATCHES TO CC1016 FIND NO MATCH VALUES ABOVE 0.232 

CONCLUSION IT HAS NO SIBLINGS IS CORRECT
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Performance of Match Value Algorithm

Highest Accuracy of 99.85% at

Acceptance Threshold = 0.270 – 0.280

For the Match Value Algorithm used
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Examiner Cross-Spectral Review

Glock Sheering and BreechFace Marks 

in Corresponding VL and IR Images 

Segment cut from IR image overlaid on VL image demonstrates 

Similarity of Breechface and Primer Sheering Toolmarks in VL and IR

and 

Simplicity of Manual Cross-spectral comparison In spite of VL Lighting Artifact 

 and Different Resolution: Primer Diameters: 380 VL 320 IR
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ROC Comparison of Cartridge Case Matching

Based on BreechFace and Sheering Marks

Accuracy of Matching as a Function of Image Spectra:

 IR-IR VL-VL and Cross-Spectral IR-VL
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IR-ID of Damaged Bullets
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FlashCorrelation of IR Bullet Sequences:

Bullet #1 Frame #1

Bullet #2 Frame#516

Bullet #1 Frame #1529

Bullet #2 Frame #516+1529

• Same-Sequence Framewise Self-Correlation Measures Rotation Stability

• Two-Sequence Framewise Cross-Correlation Detects Suspected Siblings and

Synchronizes Sequences
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SigSauer 40 Speer S&W

30 sec imaging per 360o 

Bullet #1 Bullet #2

IR Image Sequences of Damaged Bullets 

Visual Image

Bullet #1

Visual Image

Bullet #2
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Conclusion

• Thermal IR Imaging is Characterized by Emissivity 

Effects and Shallow Depth of Focus

• Range Gated Emissivity Maps Provide Reliable 3D 

Models and Extended-Focus 2D Images

• Which have been found to produce high-accuracy ID 

of Firearms-Induced Toolmarks

• Using fully Automated Image Capture and Compare
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Questions?
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Francine Prokoski, President

 

Infrared Identification Incorporated 

POB 1038 

Lorton VA 22199-1038 

703 690 1234 

Thank you! Thank you!