1. Shoot-Around
Reflect on yesterday’s video: how did DNA affect the case?
Was the DNA analysis the main evidence that led detectives to the killer?
Where did CSI find DNA at the case? How was it preserved? Analyzed?

2. DNA is the Genetic Material
Forensic DNA Analysis
DNA is the Genetic Material

3. Topic: DNA at a Crime Scene
Objective: SWBAT identify sources of DNA at a crime scene and how they are preserved and initially analyzed in a lab

4. Question: What are the sources of DNA?

5. Sources of DNA Saliva Blood Tissue Urine Semen Hair Feces Bone Teeth
Skin Cells
Sweat

6. Where should we look for DNA?

7. Critical to Locate Evidence
It is important to have good crime scene analysis.
Evidence technicians, trained in DNA work, extract material from evidence. (BS in Science)
Crime Scene analysts identify evidence at the crime itself. (BS in Criminal Justice)
Forensic DNA analysts extract the DNA and perform the reactions and analyze the results. (MS in science)

8. A reference sample
A reference sample is required to identify matches between DNA. Unless, there is a sample already in the CODIS system, we will need to find one!

9. Reference Samples Blood Blood transfusions Buccal Swabs/Saliva
Clothing
Last resort secondary standard
Other Secondary Standards
Toothbrush, hairbrush, glasses, etc.
Other standards
All persons who had access to a crime scene should be documented
May be necessary to collect samples from these individuals

10. How do we process the evidence?

11. Case Processing Includes: Location and Collection of Evidence
Collection Techniques
Preservation of Evidence
Packaging and Storage
Documentation-Chain of Custody
Casework Analysis
Collection with cuttings/swabs, Evidence is preserved both before you get it and when you are finished with it, we document the packaging we receive and item in, seals, and we package our collected evidence in coin envelopes, we document our results, as well as who has the evidence at all times; Once we are done, we analyze our results recheck to be sure we did everything right, and send out our report to the submitting agency

12. Protect the Evidence Preserve evidence with proper packaging
Proper storage
Use appropriate labels
BIOHAZARD LABELS
Case#, Initials, Descriptive label, date packaged
Sign across your seal!!

13. Evidence Handling
Never collect evidence without documenting the location, conditions, etc first
Sketches, photographs, detailed notes
The fewer people who handle evidence, the better
Decreases chance of contamination
Assists in court admissibility hearing

14. Chain of Custody
A record of individuals who have had PHYSICAL possession of the evidence
Critical in maintaining the integrity of the evidence
If DNA analysis results in a foreign DNA type, it may be necessary to identify persons who handled the evidence
A couple of ways that different labs keep chain of custody documentation

15. Chain of Custody Components
Identifiers that describe the evidence at the time it was found
Location
Position
Date/Time of Collection
Packaging/Sealing information
What type of packaging, tape used to seal, any damage to packaging?

16. Multi-Section Cases
Many items need to go through other sections of the lab
Common requests:
Latent Prints
Trace / Microanalysis
Firearms
Important to decide based on case, which evidence has priority

17. How Can Evidence Become Contaminated?

18. Actions to Avoid Touching any areas/items where DNA may exist
Touching your face, nose, hair, and mouth when collecting and packaging evidence
Sneezing, coughing, excessive talking near evidence
Gloves and or masks should be changed if contaminated
Touching some parts of evidence is unavoidable in handling evidence, but avoid touching areas where you really expect to find DNA
We had an intern in the lab who could not stop scratching her nose for anything
It’s natural to talk while you are working in the lab. But excessive talking especially above the evidence can lead contamination and interrupting concentration

19. Summary
In the summary box, write 2-3 that summarizes this section. Make sure to reference where DNA is located, preserved, and processed.