Lecture 2 - CSI and Physical Evidence Considerations Flashcards
Most crime labs suffer from too much evidence. Too much clothing, too many cigarette butts, too much glass, COVID masks, etc.
ALS doesn’t detect everything
Samples can be present in really small quantities. Also, other bodily fluids show up under luminol that may not be relevant to the investigation. And it can’t be distinguished from blood, etc.
Two big decisions with evidence
Deciding what gets collected - CSIs and law enforcement
Deciding what gets sent to and analyzed by the lab. - Law enforcement, DA, forensic lab, defense attorney, others. Crime Lab Directors, those facing pressure
Cases where the crime lab can push back:
couch example: Touch DNA is low quality
Too many people have been on that couch
You’d need to submit a whole couch
Other contaminants
Fibers complicate process
Lab could push back. However, this involves a minor and assault. High-profile. So the lab will run it. Same with homicide.
Anthrax Example
There is a huge push for techniques that can pre-screen DNA. Because most DNA collected gives nothing. Determine which ones have DNA, etc. before testing.
Instead of DNA extraction first. ALS? Immunoassay? SNPs? Cell charac? Fluorescence?
DNA profiling is a two to three day process. 1000 dollars/sample. His opinion: publicly funded crime labs, backlog is mostly due to time, not always money.
Once identified, physical evidence is packed and stored carefully. PPE is used to avoid contamination.
Two big enemies with DNA
heat, moisture (water). Water is bigger than heat. Needs to be properly vented if wet.
Forensic Labs all over the country have diff capabilities - depending on equipment/facilities, funding, staff, expertise.
Public Crime
City/County
Regional
State
Federal
Private Commercial
Toxicology
DNA/ Serology
Firearms/Toolmarks
University Labs (ad hoc analyses)
-Special Circumstances
Anthropology
* Toxicology
* Chemical profiling (e.g., isotopes)
Forensic Laboratories
Criminalistics
- basic
- expanded
specialized services
Basic Crime Lab Services (Publicly Funded)
Physical Science/Trace Unit
Biological Unit
Firearms/Tool Marks
Photography Unit
Fingerprint Unit