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

2009©Forensic Science Today

Serology

Body fluids and the stains they leave at crime scenes


Common Types of Serology

Commonly found rape cases are: Blood Hair Sperm


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.


True or False

No two individuals, except for identical twins, could be expected to have the same combination of blood factors.


Prior to 1990, A-B-O system provided the best means for forensic scientists to link blood to an individual.

What changed in 1990?


Components of Blood

Cellular-Solid materials suspended in plasma that makes up 45% of “blood” Red Blood Cells (RBC)-erythrocytes White Blood Cells (WBC)-leukocytes Platelets

Plasma – 55%- fluid portion of unclotted blood-mostly water Antibodies Enzymes Proteins

Serum= liquid that separates from the blood when a clot is formed


Blood Stains on Victim’s JeansSections removed & initialed for testing


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?


Species Identification

Prior to 1990, double immuno-diffusion plate was used for species identification of blood stains.

Today scientists simply test using DNA techniques


Techniques to Visualize Kastle-Meyer – uses H2O2 +

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.


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.


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 http://www.flickr.com/photos/jackofspades/4376209354/ Figure 12-5 p. 337 Saferstein Criminalistics, 2004


A Bloody Knife from a Homicide Scene.


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 diffusionSee pp. 338-339 Saferstein, Criminalistics, 2004.


Applications of Genotyping Blood Factors

No direct relevance to Criminal Investigations

Paternity Testing Blood type may clear a suspectExample: Child is type ABMother is type AB Suspected Father is type ODraw the Punnett Square.


Rape Statistics

http://www.rainn.org/statistics


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.

http://www.houstonpi.com/sementrace/videos.html


Microscopic Examination

Semen can be identified by the presence of spermatazoa @ 400x magnification


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)


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. . . .


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


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.


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

testingSee Saferstein, Criminalistics, 2004, p. 353


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


DNA Testing

Extremely sensitive- characterization possible with only 1 billionth of a gram of sample


Timing Sperm can survive up to 4-6 hours in the

vaginal cavity of a living female. Time of sexual attack may be determined. Nonmotile sperm may be found up to 3

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