2. Forensic Characterization of Bloodstains cont’d
Micro Crystal Tests
Takayama
Tiechman
Advantages
More specific then chemical test
Disadvantages
Not as sensitive
More susceptible to interference

3. Forensic Characterization of Bloodstains: Individualizing
ABO Blood Typing
Enzyme Typing
DNA Analysis
RFLP: Restriction Fragment Length Polymorphism
STR: Short Tandem Repeats
Ancient

4. Forensic Characterization of Semen: 1. VISUALIZATION
MANY BODY FLUIDS FLUORESCE WITH ALTERNATE LIGHTING SOURCES

5. Forensic Characterization of Semen: 2. PRESUMPTIVE TESTING
ACID PHOSPHATASE ENZYME /
FOUND IN LARGE CONCENTRATIONS
IN SEMEN

6. Forensic Characterization of Semen: 3. CONFIRMATION
A. MICROSCOPIC IDENTIFICATION OF SPERM
B. DETECTION OF P30, A MALE PROSTATE PROTEIN. USEFULL FOR VASECTOMIZED MALES

7. Intact spermatozoa on a vaginal slide

8. Forensic Characterization of Saliva
Detection of Amylase
(breaks down starch in gel)
Evidence commonly tested for the presence of saliva includes:
Cigarette butts
Envelope flaps
Swabs taken from the body of sexual assault victims
Bottles, cans, & straws
Gel contains starch that is broken down (circles ) in the presence of Amylase enzyme

9. Safety First—safeguards while handling biological evidence
Wear gloves
Keep contaminated surface away from face—protect those mucous membranes
Properly dispose of gloves/wash hands

10. Goals of biological evidence collection
Collect as much sample as possible from a single source—keep it concentrated
Ensure that the sample is not inadvertently mixed with other biological samples—change gloves if contaminated
Handle the sample in a manner that minimizes deterioration—air-dry quickly (and no heat or sunlight exposure)

11. Further recommendations for collection of biological evidence
Handle as little as possible—submit the item with the stain still on it
If stain is on a large porous surface (e.g., a rug) cut out the stain area (plus unstained)
Collect with slightly moistened (with dist. water) cotton swab—keep it concentrated, and take a control swab too

12. Taking care to avoid contamination
Don’t allow one evidence stain to come into contact with other biological samples, including transfer from tools and gloves
Don’t talk or cough over evidence stains
Collect and package stains separately
Clean tools (e.g., tweezers) thoroughly, with distilled water stream, dry with tissue, repeat
May use disposable tools

13. Packaging biological evidence
Allow stains to air-dry as much as possible before placing in paper bag or envelope—do not use plastic
Use separate paper containers for each item and package stains and controls separately
Ensure that the paper container is large enough to allow circulation around the evidence item
For garments, use clean paper to prevent different stains from contacting each other

14. Proper collection and procedures are critical to avoid Contamination How else will you detect it and reduce/avoid contamination?

15. Typically, it looks like a mixture:
A combination of DNA from two/more persons

16. Contamination at autopsy—teeth from decomposed body

17. Contamination at autopsy—mixed reference

18. Contamination at autopsy—resolution

19. Contamination in the lab
To sample with low level of DNA
From sample with high level of DNA

20. PCR Product Contamination—the Thousand to One Nightmare
It only takes a minuscule amount of amplified product…
…to cause a typing disaster

21. Contamination—Prevention
Sample items one-at-a-time
Separate evidence samples from reference samples
Use protective gear
Separate work areas with dedicated equipment

22. Monitoring for Contamination—Controls ‘R’ Us
Bloodstain (Evidence)
Substrate Control
Reagent Blank—for Evidence
Victim’s Reference Sample
Reagent Blank—for References
Negative Amplification Control
Quality Control Sample
Positive Amplification Control

23. Summary 1
Screening samples for biological evidence includes both physical (e.g. alternate light sources) and chemical (presumptive tests) detection methods.
3 steps- Visualization, Presumptive testing and Confirmation
Blood detection include observation of color, microcrystalline tests, luminol detection, chemical presumptive tests based on hemoglobin's peroxidase-like activity, antibody species tests, and DNA analysis.
Semen detection includes observation of fluorescence, Acid phosphatase detection methods, then microscopic examination, P30 testing and DNA
Saliva detection includes microscopic examination, amylase detection and DNA

24. Summary 2
Safety- In collecting biological evidence, safety is paramount. Wear gloves- away from face- Properly dispose of gloves/wash hands
Collect as much sample as possible - keep it concentrated- not inadvertently mixed -change gloves if contaminated
Handle the sample in a manner that minimizes deterioration—air-dry quickly (and no heat or sunlight exposure)
Prevent contamination- Sample items one-at-a-time- Separate evidence samples from reference samples- Use protective gear- Separate work areas with dedicated equipment- Clean the area, tools and run QC
Monitor for contamination with controls