Biological Evidence Flashcards
Good Sources of DNA
blood, semen, tissue
Serology Tests and Results
Negative - did not indicate the presence
Presumptive positive – indicates the
presence
Inconclusive – it may or may not be…
Confirmatory – spermatozoa were
observed
Touch DNA
Sources:
Skin Cells
Perspiration
Nuclear DNA
- examine 23 locations
- (two are male-specific) + a sex
- determining marker (XX/XY Amelogenin)
of the DNA
Mitochondrial DNA
Looks at maternal DNA (Mom’s
DNA) found in the mitochondria
of a cell
Good for old cases, hair analysis, skeletal remains
(YSTRs) DNA
Looks at paternal DNA (Dad’s DNA) found on the Y chromosome
DNA Results
- DNA from one contributor
- DNA from two or more contributors
- Inclusion or Match
- Exclusion or “No Match”
- Inconclusive or Uninterpretable
- No Results
Likelihood Ratio (LR)
Compares two probabilities to find out which of the two probabilities is the most
likely.
Counting Method
gives the expected frequency of a YSTR profile based on a database search.
CODIS
- Combined DNA Index System
- Developed and maintained by the FBI
T/F
CODIS will NOT accept: Profiles of victims and individuals other than the perpetrator who can be associated to the victims (i.e., husbands, boyfriends, roommates) or
individuals not associated with the crime
T
Which items best answer
the investigative questions?
Representative samples
Buccal Swabs
Collected from victims, suspects, and others as part of the criminal investigation process
Property Crimes Submitting guidelines:
Limit of 2 samples
No limit on references
May submit more if multiple scenes or
suspects
Violent/Person Crimes Submitting guidelines:
Submit actual item instead of swabbing
If item too large to transport or to store
in evidence vault, swab or cut stained
area at scene
Obtain all necessary references
Call lab to discuss evidence prior to
submission
