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2009©Forensic Science Today Serology Body fluids and the stains they leave at crime scenes.

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Presentation on theme: "2009©Forensic Science Today Serology Body fluids and the stains they leave at crime scenes."— Presentation transcript:

1 2009©Forensic Science Today Serology Body fluids and the stains they leave at crime scenes

2 2009©Forensic Science Today Common Types of Serology  Commonly found rape cases are: Blood Hair Sperm

3 2009©Forensic Science Today History of Blood Typing  1901- Karl Landsteiner, recognized differences in human blood Received Nobel Prize in 1929  Critical in blood transfusions  A-B-O classification system  Rh factor in blood was demonstrated in 1937  More than 100 different blood factors are known today.

4 2009©Forensic Science Today True or False NNo two individuals, except for identical twins, could be expected to have the same combination of blood factors.

5 2009©Forensic Science Today Prior to 1990, A-B-O system provided the best means for forensic scientists to link blood to an individual. What changed in 1990?

6 2009©Forensic Science Today Components of Blood CCellular-Solid materials suspended in plasma that makes up 45% of “blood” Red Blood Cells (RBC)-erythrocytes White Blood Cells (WBC)-leukocytes Platelets PPlasma – 55%- fluid portion of unclotted blood-mostly water Antibodies Enzymes Proteins Serum= liquid that separates from the blood when a clot is formed

7 2009©Forensic Science Today Blood Stains on Victim’s Jeans Sections removed & initialed for testing

8 2009©Forensic Science Today Forensic Characterization of Bloodstains  Is it blood?  From what species did it originate?  If the blood is of human origin, how closely can it be associated to a particular individual?

9 2009©Forensic Science Today Species Identification  Prior to 1990, double immuno- diffusion plate was used for species identification of blood stains.  Today scientists simply test using DNA techniques

10 2009©Forensic Science Today Techniques to Visualize  Kastle-Meyer – uses H 2 O 2 + phenolphthalein to produce a bright pink color in the detection of peroxidase activity in blood  Leucomalachite green. Leucomalacite green is dropped on the suspect stain. A positive blood result will immediately turn the swab greenish- blue.

11 2009©Forensic Science Today More Visualization  Tetramethylbenzidine- test by placing drops on a suspect stain. A positive reaction is indicated by an intense blue color.  Luminol- Luminol is also a field test that you may have seen on one of the forensic investigation television shows. It involves spraying the chemical onto the suspected bloodstain and viewing it in total darkness. If blood is present, it will begin to luminesce (glow a whitish-blue) within 5 seconds.

12 2009©Forensic Science Today Luminol Test  Extremely Sensitive- capable of detecting bloodstains diluted up to 300,000 times  Large areas are sprayed and viewed in darkened areas for emission of light  Does not interfere with subsequent DNA testing   Figure 12-5 p. 337 Saferstein Criminalistics, 2004

13 2009©Forensic Science Today A Bloody Knife from a Homicide Scene.

14 2009©Forensic Science Today From what species did it originate?  Preciptin Test >Very sensitive >Requires only a small sample >Even dried bloodstains from 10-15 years ago can be tested. >Positive test results even in diluted samples  Gel diffusion See pp. 338-339 Saferstein, Criminalistics, 2004.

15 2009©Forensic Science Today Applications of Genotyping Blood Factors  No direct relevance to Criminal Investigations  Paternity Testing Blood type may clear a suspect Example: Child is type AB Mother is type AB Suspected Father is type O Draw the Punnett Square.

16 2009©Forensic Science Today Rape Statistics 

17 2009©Forensic Science Today Forensic Characterization of Semen  Locate the stain and screen for semen with the acid phosphatase color test  Acid phosphatase is an enzyme present in high concentrations in semen  Suspect stain is transferred to filter paper; reagent is added. If semen is present, sample will fluoresce under UV light within 30 seconds. 

18 2009©Forensic Science Today Microscopic Examination  Semen can be identified by the presence of spermatazoa @ 400x magnification

19 2009©Forensic Science Today Challenges for the Microscopist  Sample collection: Sperm bind tightly to cloth materials, are extremely brittle when dry, and disintegrate if the stain is washed or rubbed against another object  Oligospermia – abnormally low sperm count (prefix Oligo means “just a few or scant”  Aspermia - absence of sperm or sterility (partly due to growing popularity of vasectomies)

20 2009©Forensic Science Today p30 or Prostate Specific Antigen  Protein discovered in 1970’s  Unique to seminal plasma  See Criminalistics pp. 351 & 352 Figure 12-6 and Figure 12-17 for PSA testing by precipitation and electrophoresis  If semen is present, DNA testing is used to link seminal material to an individual. More later....

21 2009©Forensic Science Today Collection of Rape Evidence  Forceful physical contact between victim and assailant may result in the transfer of hair, fibers, blood, and semen (Locard’s Exchange Principle)  Carefully package all outer garments and undergarments separately in PAPER bags.  Victim should stand on paper while undressing so that any loose fibers can be collected for analysis.  Collect bedding, if appropriate

22 2009©Forensic Science Today Collection of Rape Evidence  Disposable latex gloves are essential for handling evidence!  DNA may be transferred through perspiration. Investigators must avoid direct personal contact with evidence.

23 2009©Forensic Science Today Victim needs a medical exam ASAP! Evidence collection kit includes  Pubic combings & standard/reference samples  External genital skin areas  Vaginal swabs & smear  Cervix swabs  Rectal swabs & smear  Oral swabs & smear  Head hairs  Blood sample  Fingernail scrapings  All clothing  Urine specimen (for drug testing e.g. Rohypnol, GHB)  Swab of any area that may have assailant’s saliva for DNA testing See Saferstein, Criminalistics, 2004, p. 353

24 2009©Forensic Science Today Evidence from Suspect, if apprehended  All clothing  Pubic Hair combings  Pulled head and pubic hair standard/reference samples  Penile swab taken within 24 hours after assault  Blood sample or buccal swab for DNA testing

25 2009©Forensic Science Today DNA Testing  Extremely sensitive- characterization possible with only 1 billionth of a gram of sample

26 2009©Forensic Science Today Timing SSperm can survive up to 4-6 hours in the vaginal cavity of a living female. Time of sexual attack may be determined. NNonmotile sperm may be found up to 3 days after intercourse. AAcid phosphatase can be detected in the vaginal cavity for up to 48 hours after intercourse. p30 can be detected for 24 hours.


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