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?

DNA is the Genetic Material Forensic DNA Analysis DNA is the Genetic Material

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

Question: What are the sources of DNA?

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

Where should we look for DNA?

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)

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!

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

How do we process the evidence?

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

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!!

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

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

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?

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

How Can Evidence Become Contaminated?

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

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