DNA
Evidence Identification, 
Collection & Preservation 
For Law Enforcement 
 

Presidential Initiative
March 11, 2003 

 Initiative to Advance Justice Through DNA 
Technology 

 6 different DNA issues to include training for 
law enforcement officers 

 The result is critical pieces of evidence will be
collected, fewer cases will be jeopardized by
mishandling and more cases could be solved.


Purpose 
Utilize available technologies 
Improve conviction rates 
Exonerate the innocent 


DNA Evidence and Bio-safety 


Universal Precautions

 Treat every item as though it were 
contaminated with blood or other body fluids 

 Use Personal Protective Equipment 

 Face mask/shields 

 Safety glasses 

 Gloves 

 Disposable cover-alls 

 Shoe covers 


Contamination Practices

 Educating crime scene personnel 
   touch evidence 
   clean practices 

 If possible, use disposable instruments to 
pick up items 

 Otherwise, clean items with 10% bleach & 
alcohol between samples 

 Try not to touch the area you want tested!


Contamination Practices

 Use of cell phones in the crime scene 
may result in inadvertent contamination 
of an item if gloves have not been 
changed 

 Change gloves with EVERY item! 

 No smoking IN the crime scene 


The Crime Scene 
Proper Collection, 
Packaging & Preservation 
of DNA Evidence 



Securing the Scene 
Identify focal point of scene and 
extend outward to establish scene 
boundaries 


Securing the Scene 

 Limit number of people with access to scene 

 Keep log of all personnel that had access 
to the scene  for elimination samples 


Image of Stop sign with crime scene contamination tips
 


Documentation 
 Essential to establish: 
 Location 
 Condition 
 Chain of custody for each item collected 



Types of Documentation 
 Notes 
 Diagrams 
 Photographs 
 Video and audio 


Potential Sources of DNA Evidence

 Clothing 
 Hat/Cap sweatbands
 Eyeglasses 
 Earrings 
 Chewing gum 
Toothpicks 
 Toothbrushes 
Food 
 Bottles or cans
 Water bottles
 Gloves 
 Watches 
 Condoms 
 Bite/Lick/Suck marks 
 Used tissues 
 Licked stamps 
 Handkerchiefs
 Envelopes 
 Cigarette butts 


Common DNA Sources 
Blood
 Victim or Suspects body 
 Weapons 
 Clothing 
 Other items at scene or transported away from scene 
 


Common DNA Sources
Semen  
 Victim/Suspects body 
 Clothing 
 Towels 
 Bedding 
 Condoms/devices 


 
Common DNA Sources
Vaginal Fluid  
 Suspects pubic area 
 Suspects underpants 
 Suspects fingers 
 Condoms 
 Devices 



Common DNA Sources
Saliva 
 Victim or Suspects body 
 Underpants 
 Expectorant 
 Bitemarks 
 See Oral evidence 
 


Common DNA Sources 
Oral 
 Items coming in contact with someones mouth 
 Items left behind by V or S 
 Careful!! Consider the probative nature of time, 
location, and mobility!! 


 
Common DNA Sources 
Hairs
 Individuals pubic area 
 Clothing 
 Crime scene 
 


Recognition of Hairs/Fibers 
 Consider the probative nature of hairs/fibers 
 Domestic situations 
 Boyfriend-girlfriend 
 Use oblique lighting 



DNA Sources 
Urine and Feces
 Victim and Suspect underpants (sodomy) 
 B&E scenes 
 Vandalism scenes 
 

24 
DNA Sources
Touch 
 Casual contact between a persons hand(s) and an item 
 GLOVES?? 
 Intentional use, unintentional DNA loss 
 MIXTURES!! 
 


Caution Regarding Touch DNA

 Carefully weigh the value of a 
possible latent print against a 
possible DNA profile 

 Touch DNA is not meant to 
replace latent prints! 


 
DNA Sources
Wearer  
Items that are: 
 In contact with a persons body 
 Items left behind by V to mark location 
 Items discarded by S (inadvertently or not) 
 Careful!! Consider the probative nature of time, 
location, and mobility!! 


Knowledge into Practice

 Look at the following crime 
scene photos and identify the 
following: 
  Salivary DNA sources 
  Probative touch DNA sources
  Probative wearer DNA sources



Knowledge into Practice 
Image of bathroom



Knowledge into Practice 
Image of car in woods



Knowledge into Practice
Image of bank
 

 
Knowledge into Practice
Image of clothes strewn on bushes
 

 
Knowledge into Practice 
 Look at the following pictures and identify 
potential sources of DNA 


 
Knowledge into Practice 
Image of childs bedroom



On-Scene Blood Detection

 Visually 
   Look for red/brown/green/black stains

Luminol/Bluestar 
   Quick and easy screening tool when blood may be present BUT IS NOT VISIBLE! 


Before 
Image of carpet


After
Image of carpet with lumniol 


Before 
Image of fabirc


After
Image of fabric with luminol
 


BLUESTAR
Image of wood without bluestar
Image of wood with bluestar



BLUESTAR
Image of road without bluestar
Image of road with bluestar
 

41 
Luminol/Bluestar 
   Advantages 
   Screening tool 
   Sensitive 
   Easy to use 

 Talk to YOUR laboratory! 

Caution!!

 Chemical screening tools are not specific for blood 
 Metals, bleach, cleaning products, treated lumber, animal fat, and itself 
 Always examine positive reactions and surrounding areas in regular light 
for visible staining 
 If blood-like stains are seen,DO NOT use! 



On-Scene Detection of Semen 
 Visually 
White or cream-colored stains 


44 
On-Scene Detection of Semen 
 Alternate light sources (ALS) 
 UV, Omnichrome, Luma-Lite, Crimescope,CrimeLite 


 
ALS Principle 
 Different substances react differently to light 



Detectable Body Fluids 

Urine 
Semen 
Saliva 
Vaginal Secretions 
Sweat 


ALS Rules

 Semen stains reflect specific light 
differently than the background fabric 
   May be darker than the background 
   May be lighter than the background 


Light Sources 

 Location/screening use 
   Not confirmatory 
   Detection ability based on fluid & fabric 

 All ALS stains NOT semen stains 
 All semen stains NOT detected with ALS 


False Positives
 Laundry detergents: 
   Contain phosphors (appear brighter in sunlight) 
     Sunlight contains UV light making whites whiter 
     Dark pigments absorb the UV light and dont glow 


What to Collect 

 Anything to link suspect, victim, weapon, crime scene 
 Anything to clarify what happened
 Known Standards 
    Blood or oral swab 
    Hair 
    Control area 


Known Standards

 Known victim, suspect, and elimination samples: 
   Eliminates the need for repeated analyses 
   Enables a more discriminating search of the data bank 
   Ensures that its the suspects profile being searched 
   Enables more discriminating statistics and conclusions 


Control Swabs

 An unstained area near the stain collected 
 Check with your laboratory regarding their preference for 
collecting control swabs  


53 
Small or Mobile Items 

Collect and submit entire item 
Knife 
Shoe 
Hat 


 
Large or Immobile Items 
Submit portion of items 
 Cutting: carpet, car seat 
 Swabbing: linoleum 
 Lifting: glass, counter top 
 Scraping: cement wall 
 Absorbing: wet blood 


Probative Value 

 DNA is a very stable molecule and
can remain intact for many years

 Not every item at a crime scene 
should be considered probative 
evidence 



Probative Value 
 The best evidence occurs 

When a victims or suspects DNA is found 
where it is not supposed to 
be 



Packaging of Evidence 
 Dry items should be packaged in porous containers 
such as paper bags, envelopes, boxes 


Packaging of Evidence 

 Wet items should be allowed to air dry prior to packaging 

 Very wet items can be transported in plastic containers 
but should be air-dried as soon as possible 


Chain of Custody 

 Key to the proper resolution of a criminal investigation 

 All the work in the lab is meaningless if the chronological 
history of the evidence is not maintained 



Transportation of Evidence

 Extended exposure to heat or humidity causes degradation 
to biological evidence 

 Packaged items from the crime scene need to be moved to a 
suitable storage facility as soon as possible 


61 
Transportation of Evidence 

 Liquid samples should be transported in refrigerated or 
insulated containers 

 Evidence should be stored in a temperature controlled facility 


Evidence Storage 

 The hallmarks of proper evidence storage include: 
    Paper packaging 
    Items are sealed 
    Items from a single case are kept together when possible 
    Items are kept away from heat sources 
    Chain of Custody is current 



Collection of Evidence Proper Collection, Packaging 
& Preservation of DNA Evidence 



Rule of Thumb 
 Its better to collect it and not submit it 
than to not have collected it at all! 

 Keep lines of communication open 
between you and the laboratory 



Amount to Collect 
 Early DNA - Size of quarter 
 Serology - Size of dime 
 Current DNA - If you can see it, we can try it 


Collection of Blood 

 Evaluate the item/stain and its probative value 
 Swab the stain (works best on non-absorbent surfaces) 
 Scrape the stain 
 Cut the stain from the item
 Collect the item 


Swabbing the Stain

 Lightly moisten the swab (distilled or sterile water) 
 Rub swab over the stain, rotating swab 
 Use 2 - 4 more swabs 


 
Swabbing the Stain 
 Concentrated!! 
 Better to collect it and not use it rather than to lose the sample 
altogether 
 Dont sacrifice other exams!! (latents!) 


Collecting the Item 
 Recommended 
   When staining pattern is important 
   Item is difficult to swab 
   Item requires multiple exams 
 Make sure the item is dry 
 Package to ensure integrity (glass, sharps, breakables) 



Collection of Semen
 Evaluate the stain and its probative value 
 Swab the stain 
   Works best on non-absorbent surfaces 
 Cut the stain from the item 
 Collect the item 


Possible Victim Vaginal Fluid

 From suspect pubic area or fingers 
 Lightly moisten the swab (distilled or sterile) 
 Swab the entire area, rotating the swab 
 Use no more than 2 swabs 


Victim Sexual Assault Kit

 Standardized kit to collect pertinent biological 
evidence from the body of the victim 
 Contact your local laboratory to determine 
which kit they use 



Suspect Standard Kit

 Standardized kit to collect pertinent biological evidence from 
the body of the suspect 
 Contact your local laboratory to determine which kit they use



Collection of Hairs/Fibers
 Post-It notes placed into envelope or Ziploc bag
 Straight into Ziploc bag NOT recommended due to static electricity 
 Gloves or forceps to transfer hair/fiber(s) into a glassine envelope
 Vacuum is generally not recommended 
 Talk to YOUR laboratory! 


Collection of Saliva

 From a bitemark: 
   Moisten one swab and swab area of mark 
   Follow with a dry swab to collect any 
    remaining moisture on skin 
   Allow swabs to air dry and package together 
 From Suspect Pubic Area 
   Refer to vaginal fluid instructions


Known Saliva (Buccal) Swabs 

 Known standard 
 Swab the inside of the cheek area using 2 swabs 
 Rotating them during collection 
 Allow swabs to air dry (or place in swab box) and package together 


Fingernail Scrapings/Clippings

 Collect only when indicated 
 Clip nails into clean paper with a cleanclipper
 Separating left and right nails 

OR 

 Scrape the underside of each nail onto a clean paper
 Package the scrapers inside this paper 


Bone

 Co-mingled remains, mass graves, skeletal remains, exhumations, 
airplane crashes 
 Marrow is where blood is made 
 Good to use if no blood is available 
 Best to collect rib bone or vertebrae 
 Place in jar and freeze 


Teeth
 DNA is in the dental pulp 
 Very resistant to decay 
 Obtained from teeth of mummies 
 Saved baby teeth can be used as 
secondary DNA standard in missing 
person cases 
 Collect into pill box 



Organs/Tissue 
 Collect if no blood is available 
 Collect liver or spleen 
 Place in jar and freeze 



Data Bank Samples 
 Follow your state or local protocol for collecting samples 
from arrestees and/or convicted offenders 



Knowledge into Practice 
 Look at the following items and determine 
the best way to handle the object 


Knowledge into Practice
Image of hammer and chisle
 

Knowledge into Practice
Image of hair on clothing 


Knowledge into Practice 
Image of cigarette butt by doorway


Knowledge into Practice
Image of wrist watch
 

Knowledge into Practice
Image of object with stain
 

Knowledge into Practice
Image of ski cap in garden
 

Knowledge into Practice 
Image of chweing gum


 
Knowledge into Practice 

 For the following items, indicate how 
you would collect the evidence 


Knowledge into Practice 
Image of stone walkway


Knowledge into Practice
Image of stain on car window
 

Knowledge into Practice
Image of broken window with blood 
 


Packaging Materials
 Paper bags 
 Plastic bags* 
 Pill boxes 
 Envelopes and note pad 
 Paint cans 
 Cardboard boxes
 Evidence tape 
 Specializedmaterials
 Glass jars 



Packaging Techniques 
Choice of proper container 
 Paper is the packaging material of choice 
 Plastic should only be used when there is danger of liquids 
(biohazard or other) penetrating 



Packaging Techniques 
Air-Dried 
 Evidence should be allowed to air-dry 
 The optimal method to preserve DNA 


Packaging Techniques 
Tissue and liquid samples 
Keep refrigerated 



Caution!! 
Never freeze liquid tubes of blood 
Be careful, put glass tubes in plastic bag 


Packaging Techniques 

 
Package items separately when recovered separately 
 If items found together, then package together 
    Clothing in a pile 
    Cigarettes in an ashtray 


Packaging Techniques 
 Dont allow fluids or stains to 
touch each other or unaffected areas 


Packaging Techniques 
Minimize interior movement 



Packaging DNA Evidence 

Unacceptable 
 Plastic 
 Multiple items per bag 
 Stains still wet 
 Mummy wrap 

Acceptable 
 Paper 
 One item per bag 
 Stains air-dried 
 Do not overfill bag 


Labeling Packages

 Name/initials of the collector 
 Each person/entity subsequently having custody 
 Date of collection or transfer 
 Agency and case # 
 Victim or suspect name 
 Brief description of item 


Labeling Packages 
 Label container before packaging 


 
Labeling Packages 
 Label and identify exterior as to content 


 
Labeling Packages 
 Label the item with warnings/hazards or other helpful information: 
    Biohazard 
    Sharp 
    Fragile 
    Unloaded 
    Etc. 


Sealing the Package

 Seal packages with tape 
 Prevents items from falling in 
 Prevents items from falling out
 Provides measure of security  evidence cant be accessed 
unless seal is broken 
 Initial across seal or under the seal 



Sealing the Package 
Acceptable 
 Scotch tape 
 Packaging tape 

Unacceptable 
 Masking tape 
 Staples 


Identify the Packaging Error
Image of cigarette butt in plastic 


Identify the Packaging Error 
Image of knife sticking through paper bag

 
Identify the Packaging Error 
Image of 2 cotton swabs in same plastic bag
Image of 2 dna swabs in same plastic bag


Preserving DNA Evidence 
Acceptable 
 Keep cool 
Bring to lab as soon as possible 

Unacceptable 
 Keep warm 
Delay in transport to lab 



Trunk Storage 

Summary 

DO 

 Air dry before packaging 
 Use paper 
 Use separate bags 
 Use plenty of room 
 Seal with scotch tape 
 Initial with permanent marker 
 Keep item cool 


Summary

DONT 
 Package item still wet 
 Use plastic 
 Clump in one bag 
 Use smallest bag
Staple shut
 Initial with ballpoint pen 
 Keep in trunk in July 


Now What?
 Are you familiar with your labs DNAtesting policies? 
 Do they 
   Work all types of cases? 
   Work cases regardless of the submissionof a suspect sample? 
   Work both subject and non-subject cases? 

 Contact lab personnel for assistance inevaluating evidence with 
respect to the labs policies and capabilities 


Time to Submit!

 Follow your agencys and forensic labs policies 
   Meet in person? 
   Submit only pre-approved items? 
   Special times & locations for submission?
   Specific directions? 
   Prioritization? 
     i.e., if you get results on A, dont worry about B. 

 Continue the investigation while waiting for results! 


Laboratory Analysis 
Proper Collection, 
Packaging and Preservation 
of DNA Evidence 


Where is DNA Found? 
Epithelial cell 
Sperm cell 
Tissue cells 
White blood cells 


Typically Encountered Samples 
Image of cotton swab, blood spatter, blood vials, clothing, semen


Evidence Screening
Image of technician
 

Blood Examination

*Never assume a red stain is blood*
   Presumptive testing 
   Confirmatory testing 
   Human origin testing 

*Cannot tell age of a bloodstain* 


DNA Blood Facts

O Located in white blood cells 

O If you can see it, we can test it 

O Transfusions do not interfere with typing


Semen - General Rules 

 Primary indicator of sexual activity 
 Begin with body swabs, then to clothing and bedding 
 With successful analysis of semen, limited 
further analysis will be performed 



Semen Examination 
 Presumptive testing 
 Confirmatory testing 
   P30 
   Sperm 

Human Sperm
Image of sperm
 

How Many Sperm?

 Average Human Male 
   Deposits 3-6 ml of semen 
   1 ml semen = > 100 million sperm 
   Possibly over 600 million sperm!!!!! 
 Vasectomized Male 
   Deposits 0 sperm 


How Long Can Sperm Last?
 Normally ~3-4 days in vaginal cavityof living woman
 Normally ~12 hours in rectal cavity of living person 
 Normally ~6 hours in oral cavity of living person


How Long Can Sperm Last?

From the Forensic Literature: 
 Found in frozen bodys vaginal cavity after 19 days 
 Found in frozen bodys rectal cavity after 3 years 
 Found in mummified bodys vaginal cavity after 3 years 


Reasons For Not Finding Sperm
 Acidic environment 
 Multiple ejaculations 
 Low sperm count 
 Time 
 Poor quality sperm 


 
Reasons For Not Finding Sperm 
 Victim bathed 
 Suspect didnt ejaculate 
 Bacteria ate them 
 It didnt happen 


DNA Semen Facts
 Found in sperm head 
 Need 100 sperm heads for testing
 Can separate sperm DNA from other cells in stain (vaginal cells) 



Saliva Examination 
 Presumptive 
  Amylase 
 No confirmatory test 



Hair Examination 
 Hair or Fiber 
 Human or animal 
 Body area 
 DNA located in root 
 Microscopic comparisons rarely performed 


Urine 

 Concentration varies, depending on time of void, dilution by fluid ingested 
Chemical detection tests are available
 Probative nature of urine 
 Epithelial cells may be used for DNA, depending on the amount 



Fecal Material 
 No serological testing for identification 
 Kits available for DNA testing from fecal material 



What is DNA? 
The Blueprint of Life 


DNA Structure and Location 
 Four bases: A, T, C, G 
 Spiral staircase (Double helix) 
 Genes and non-coding regions 
 All nucleated cells 


 
Location of DNA in the Cell
Image of mtDNA
 

Useful DNA Facts 

 Inherited 
 Same only in identical twins 
 Stays the same for life 
 Same in every cell 
 Stable in dry conditions 


DNA Analysis

 PCR amplification 
  Copies small amount of DNA 
  Look at 16 different areas of DNA 
STR Typing 
  1 in 100 million billion 
  Identity statement


 
DNA Analysis 
Step 1 
   Extract and purify DNA 
Step 2 
  Quantitate 


DNA Analysis 
Step 3 
   Amplify (make copies) 
Step 4 
  Separate and detect 


PCR Amplification of DNA 
Image of PCR amplification process



PCR Advantages 
 Requires small sample size 
 Old/degraded samples may give results 
 Can be automated 


Future of DNA Testing

 Mitochondrial DNA (mtDNA) 
 Transmitted through maternal line 
 Works on samples without nucleus (hair shafts) 


 
Future of DNA Testing 
 Y Chromosome DNA 
 Transmitted through paternal line 
 Useful in resolving DNA mixtures in sexual assaults 


Future of DNA Testing

 Automation 
 Relieve backlog 
 Process offender samples 
 Miniaturization 
 Portable, typing done at scene
 Direct access to database from scene 



Future of DNA Testing 
CODIS (Combined DNA Index System) 
 Convicted offender profiles 
 No suspect cases 
 Cold cases 


Future of DNA Testing
NDIS (National DNA Index System) 

 Re-examination of old cases where conviction was based on non-DNA evidence 


Cold Case Testing 


 
What is a Cold Case? 
cases that other investigators, 
for whatever reason, could not 
solve. 
--Bureau of Justice Assistance Bulletin 


 
Reasons for Cold Cases 
 Rising crime rates 
 Staff shortages 
 Budget restrictions 

Reasons for Cold Cases
Do more with less 
 Changing forensic laboratory policies
 Changing forensic laboratory priority/backlogs



Law Enforcement Responsibilities 
 Identify cases with remaining biological evidence 
 Of these cases, determine if material witnesses or victims are available 
 Identify statute of limitation issues 

-APRI 



Law Enforcement Responsibilities 
 Define categories of cases 
 Case review 


Cold Cases 

 Locate case files 
  Reports 
  Evidence logs 
  Forensic testing reports 
  Previously tested evidence
  Crime scene evidence containing biological evidence 


Law Enforcement Responsibilities 

Remember 
Cold hits begin the 
investigation rather than end 
the investigation! 


Cold Cases
 Evaluate probative DNA evidence & submit appropriate evidence for testing 
 Consult with prosecutor & laboratory 
 Continue investigative protocol 


Cold Cases
 Identify witness issues 
 Follow agency procedures for submitting DNA profile to CODIS 
 Prepare a John Doe warrant if applicable 


If a Cold Hit is Obtained 
 Identify other unsolved cases believed to have been committed by the same offender 
 Confirm the availability of biological evidence in those cases 
-APRI 


If a Cold Hit is Obtained
 Locate the suspect identified by the hit 
 Obtain a confirmation sample 
 Interview that suspect 
 Complete the investigation 


Unadjudicated Cold Hits 
In the event the crime cannot be 
adjudicated, it may helpful for: 
   Leverage for plea agreements 
   Evidence of other crimes/bad acts 
-APRI 


Unadjudicated Cold Hits

In the event the crime cannot be
adjudicated, it may helpful for:

 Enhancement of punishment at sentencing hearings 
 Information to withhold parole 


Evaluating Cold Cases for DNA
 Previous case activity 
   No viable suspect(s) 
   No evidence to link developed suspect(s) 

 Review the case file 
   Investigative reports 
   Photographs 
   Evidence recovered 
   Forensic reports 


Evaluating Cold Cases for DNA 

Is the original investigator of assistance? 


Locating Cold Evidence for DNA

 Locate and document the evidencepackages
   Police storage? 
   Court storage? 
   Laboratory storage? 
   Attics, desks, and vehicles? 
   Destroyed? 

 Chain of Custody? 


Evidence Evaluation

 Evaluate evidence with respect to the forensic laboratorys 
capabilities 
 Use a Forensic Scientist to assist this process! 



Evidence Consumption 
 US Supreme Court found that 
[i]n general, the destruction or failure topreserve potentially 
useful evidence doesnot constitute a violation of the due 
process clause, unless it can be shown thatthe police, the prosecutor 
or the laboratoryacted in bad faith. 

 Arizona v. Youngblood, 488 US 51 (1988) 
 Dixon v. State, 275 Ga. 232 (Georgia Supreme Court 2002) 

-APRI 


Evidence Consumption

 Half Rule observed by some laboratories 
 No more than half of the evidence sample may be consumed 
 Repeat testing? Not possible by the original laboratory 
 Check with your forensic laboratory to determine policy 


Cold Evidence

 Each item of evidence has a history  cant go back in time! 
 Unintentional historical contamination 
 Police and crime scene personnel 
 Scientists  both DNA and other examiners 
 Jurors, lawyers, and some judges! 


Overlooked Cold Evidence

 TOUCH evidence 
 Handles of weapons, ligatures, etc. 
 WEARER evidence 
 Items of clothing, masks, etc. 
 ORAL evidence 
 Bottles, utensils, etc.


Important DNA Principles To Consider
 DNA continues to degrade over time, although more slowly in cool, dry environment. 
 mtDNA may also have been used in these types of cases 


Advantages of Applying DNA to Cold Cases
 Advanced DNA capabilities 
Do more with less evidence sample
 Results are more discriminating 
    Not to be confused with accurate 
 Use of DNA Data Bank in the absence or elimination of a suspect 
State 
 National (NDIS) 


Post-Conviction Testing 


Law Enforcement Responsibilities 
 Identify which cases 
 Were closed before DNA evidence was available to the jurisdiction 
 Still have biological evidence remaining and the location of that evidence 
 Resulted in a conviction of a person who is still alive 

-APRI 


Post-Conviction Cases
 Share many of the same evidence issues as cold cases 
 Must consider possible contamination by 
   Attorneys 
   Judges 
   Juries from original trial 


How DNA Helps Solve the Crime 
Image of flow chart


Cold Case Summary 

 Computerization of DNA profiles will enable us to: 
   Solve no suspect cases 
   Connect cases that no one knows were perpetrated by 
    the same individual 


Cold Case Summary
 Its never too late torevisit cold cases
 We are able to use all parts of a human to solve crimes, from head to toe! 


CODIS 

Combined DNA Index System 

 Enables state & local crime labs 
to exchange and compare DNAprofiles electronically 


CODIS 

Contains two database files: 

 Convicted offender file 
   Contains DNA profiles of offender convicted of a qualifying offense

 Forensic file 
   Contains DNA profiles developedfrom crime scene evidence 


CODIS

 Convicted offender file match 
 Obtain warrant to confirm match 
 Forensic file match 
 Investigators from differentjurisdictions can exchange information 


CODIS
Possible outcomes: 
  Link 2 or more unsolved cases 
  Link a solved case to an unsolved case 
  Link 2 or more solved cases 



Using Results 

Understanding Hits and Misses 

The Reality of DNA evidence in our society. 


Reality vs. T.V.

 Public perception is influenced by TV.
 Crime solved and offender brought to justice within an hour 
 DNA collection at crime scenes is increasing 
 Technology improving
 DNA processing takes time! 


Public Perceptions

 Latent fingerprint technology improving 
 People expect police to locate & collect prints at crime scenes 
 With increased knowledge of DNA
 People expect DNA collection at crime scenes 


Fingerprint vs. DNA

 Swabbing for DNA anddusting for fingerprints
 Overlap conceptually but not practically 
 DNA labs able to perform more tests with less evidence 
 Fingerprint brush can transfer DNA between crimes 


Whos the Bad Guy?

 Police are taught not to leavefingerprints at a crime scene
 Its nearly impossible NOT to leave your DNA 
 Some agencies require fingerprints & DNA profiles of officers entered into databases. 


DNA Hit and Miss

HIT = a persons DNA was left at the scene 
    Friends and family leave DNA behind
    hit might not be that important.

MISS = A failure to find evidence. 
    Doesnt mean someone is not responsible for a crime. 
    The persons DNA might not be in the database. 


DNA History

 DNA collection was not possible prior to 1950s. 
 The discovery of DNA structure by Watson and Crick 
 Police able to link people to crimes 
 Failure to link a person to a crime by DNA does not mean not guilty 


Strategic Uses for DNA Evidence 
 Prove guilt 
 Exonerate the Innocent 
 Paternity Testing 


Strategic Uses for DNA Evidence

 Determine identity of human remains 
 Evolution of human populations 
   National Geographic 
 Study inherited disorders 



DNA in the Courtroom 
 Circumstantial Evidence 
    Information collected from witnesses 
    Documents pointing an individual as the perpetrator 


DNA in the Courtroom

 Physical Evidence 
    Information collected from actual objects 
   Bodies Stains 
   Weapons Fingerprints 
   Body Fluids Hairs, Fibers, etc. 


DNA in the Courtroom
 Prosecutor must present evidence to the court 
 Must prove an overall theory from evidence to jury 
 Scientific evidence is precise  


 
DNA in the Courtroom 
 Evidence can be: 
 Documents 
 Exhibits 
 Facts agreed on by both sides 
 Testimony of witnesses 



Scientific Evidence Admissibility Standards 
 Is the scientific evidence trustworthy? 
    Must demonstrate 
     accuracy (validity) 
     consistency (reliability) 

Scientific Evidence Admissibility Standards

 Frye Rule 
   U.S. v. Frye (1923) 
   Standard on accepting scientific evidence. 

 People v. Kelly (1976) 
   Proponent of the evidence must demonstrate the correct use of scientific procedures