Biological Evidence Flashcards
what is the importance of bodily fluids in forensic evidence?
provide key evidence to reach conclusions, assign relevance to DNA profiles, elucidate event timelines, and support crime scene reconstruction
what is important when collecting biological evidence?
- you must contextualize the evidence in terms of the crime scene
- assess whether the specific fluid/tissue is likely to have bee at the location
what questions must be asked when contextualizing the scene?
- what type of bodily fluid or tissue is it? how likely are you to find it there? what is the state of the stain?
- pattern of biological fluid or tissue
- location of biological fluid and tissue? can you use that to your advantage?
- how much biological fluid or tissue?
what is the actual argument in terms of bodily fluid in court?
how did it get there?
what is hypothesis 1 known as?
prosecution scenario
what is hypothesis 2 known as?
the defense scenerio
what is luminol?
detects hemoglobin and its derivatives resulting in a blue flourescence
T/F: an area that once had a bloodstain but does not anymore will still glow.
true
what are the disadvantages of luminol?
- luminescence can be faint and short-lived
- visualization must be carried out in the near darkness
what is the IABPA? what does it stand for?
organization of forensic experts for bloodstain pattern analysis.
international association of bloodstain pattern analysits
what can BPA provide?
- direction
- angle of impact
- type of wound
- distance from target
- force
- movement of items
- # of blows
- type of object used
- direction of force
- sequence of events
- handedness
what is a challenge of BPA?
accuracy and reproducability of conclusions by forensic pattern analysts
how might a bodily fluid be reported after analysis?
detected
suggested
inconclusive, or;
non detected
what is a kastle meyer test?
produces a pink colour in presence of blood
T/F: kastle-meyer tests are specific to blood
false
what is the problem with kastle meyer tests?
they are deleterious to DNA
what is an ABAcard HemaTrace test?
immunological test that can be used to confirm that blood is detected using the KM test of human origin
What is a phadebas press test?
detects saliva using the detection of amylase
T/F: phedebas test is only for saliva
false can also detect feces, perspiration, vaginal secretions, and semem
T/F: the phedebas test is confirmatory
false
what is acid phosphatase test?
reacts with acid phosphatase in sperm cells
what is the p30 test?
detects the presence of prostate-specific antigen aka p30
when is microscopy used for biological fluid identification?
semen cell detection
when might microscopy not work?
with men that have low sperm count or who may have been vasectomized
how long can semen evidence last?
~7 days
What is the problem of biological fluid analysis?
- too expensive to do all methods
- lack of sensitivity or selectivity of some methods
- scene vs. lab uses - method selection
- methods may be destructive
what are some challenges associated with looking for dna evidence?
there might be no DNA
T/F: the concepts of primary, secondary and tertiary DNA transfer have revealed cases of wrongful conviction.
true
what are the good things about DNA?
- persistence and stability of DNA on various surfaces
- properly stored DNA will last a long time
what are some bad things about DNA evidence?
environmental factors degrade DNA causing problems for data interpretation
What happens if STRs do not stay intact?
amplifications will not be successful causing partial profiles
What is a problem for forensic analysts in terms of DNA analysis?
it is very subjective and there is bias in interpreting DNA mixtures
what is CODIS?
USA DNA database: combined DNA index system
what is the problems with DNA databases?
- may take several days to get results
- dna profile may not be in the database
what is the NDDB?
national DNA data bank for Canada
is it possible to do DNA profiling at the police station?
yes, rapid DNA program developed integrated systems to allow for nontechnical personnel to use them generating DNA profiles outside labs
