jimtrue.com : school : CJT2141 : 12: Serology
Posted by Jim True on April 9, 2003 6:00 AM. Last Updated October 22, 2006 9:23 PM
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12: Serology
Classical Forensic Serology:
Primary type of blood typing prior to 1990.
- Presumptive Blood tests, - Kastle-Meyer, KM, Phenolphthalein (One of the best presumptive tests).
Comes into a question of selectivity & sensitivity. Selectivity or Specificity, False positives - which has the fewer false positives. Certain vegetable materials, cleaning fluids or metals will give a reaction that the test is positive for blood when it isn't. Phenolphthalein is probably the most SELECTIVE of the Presumptive blood tests. Presumptive blood test - could be present, might be present. Negative means no blood present.
Sensitivity is lower detection limits. Can be a very diluted sample and still test presumptively as positive. Most sensitive presumptive test is Luminol. Very good tool, but needs to be used properly. If luminol shows, you want to tentatively confirm Luminol with Phenolphthalein. Coca cola will sometimes show positive with Luminol. Bleach can also throw off the test.
- Confirmatory Blood Tests - Takayama & Teichmen, take a sample of the blood, put it on the slide and add a reagent and check the microcrystalline structure and reactive indexes. Positive for blood; it is blood.
- Species Determination - Ouchterlony, Preciptin - Confirmatory Species determination, at least towards genus of the species. Antigen/Antibody reaction starts to form.
Put sample in middle of Petri dish. Put wells of anti-species serum on the Petri dish and see which ones line up; you will see a visible mark on the Petri dish. Actual blood sample dissolved in saline and placed in center. Game wardens do Ouchterlony for poaching cases with other species determination. Mixture of blood types would show reaction with the species blood.
How do we make the anti-bodies? We take woody the Rabbit. 1/2 ml of human blood, centrifuge, inject with serum of blood, after about a week, rabbit will build antibodies in his system. Collect that sample from the ear, spin down and get anti-human serum. Immunology is the basis for this. Labs just buy the anti-serum commercially.
Definite difference between ape & human; sub-species might not generate. Precipitin test is done in a test tube. Extract of the serum is placed on bottom; antiserum on top. Zone will form. Ouchterlony is in a Petri dish.
- ABO Typing - Antigens reside ON the red blood cells, anti-bodies are in the serum. Centrifuge separates out the blood; serum will be straw colored.
Historical part of Forensic Serology (not done so much any longer):
ABO System
| A | 42% |
| B | 12% |
| AB | 3% |
| O | 43% |
Know the percentages (or highest to lowest)
Rhess system is 'negative and positive'; positive or negative on ABO Status.
Lewis, secretor status, 80% Lewis A/Secretors, 20% Lewis B/non-secretors. Can show ABO profile in body fluids besides blood: saliva, semen, vaginal fluids. Lewis B, will not show in other body fluids.
Evidence provided with A blood type; suspect has A blood type. 42% chance that ABO Typing is CLASS evidence.
A can donate ONLY to A
B can donate to B
O can donate to Everybody
AB can donate to AB
A, A Antigens, B Antibodies
B, B Antigens, A Antibodies
AB, AB Antigens, No Antibodies
O, No Antigens, Both Antibodies
Absorption Elution.
- Polymorphic Enzymes - PGM, EsD; this was another marker we could look for in blood before DNA typing came about. Electrophoresis (TLC on a horizontal plane with electrical current). 28% PGM 2-1, 52% PGM 1-1, 20% PGM 1. Create percentages of the population that would have that particular combination:
Victim: Type B, Secretor, PGM 1-1
Suspect: Type AB, Non-Secretor, PGM 1
| Victim: |
Suspect: |
| Type B |
12% |
0.12 |
Type AB |
3% |
0.03 |
| Secretor |
80% |
0.80 |
Non Secretor |
20% |
0.20 |
| PMG 1-1 |
52% |
0.52 |
PGM 1 |
20% |
0.20 |
| Total: |
4.992% |
0.04992 |
Total: |
0.12% |
0.0012 |
These percentages are multiplied together to get the relative percentage of the population that could have this combination of blood factors.
- Is it blood? (Presumptive/Confirmatory Blood Test)
- Is it Human? (Species Determination)
(All you're doing in the field is 'screening'; the lab will confirm the actual material).
- Document blood at a crime scene: Photograph, sketches and notes. Bring the whole article in, if possible.
- Collect the sample; sample and a control - qtip with drop or two of distilled water, collect the blood sample.
- Control is a qtip with distilled water, from an area where no blood appears to be present.
- Do a positive control to test your presumptive test. Verify reagent is working as control sample. Luminol is used last.
- Do visible blood evidence FIRST; luminol in total darkness for latent blood evidence. Take swab of area where luminol indicates blood; take a swab for phenolphthalien. As control for luminol. Throw a penny down on the floor and spray with luminol as control test for reagent.
Other Bodily Fluids that Serology deals with:
Semen - Problems, what if the suspect has had a vasectomy? P30, look for heads and tails. PSA, Prostrate specific antigen (PSA); look for Acid Phosphatase, tremendous amount of this acid in seminal fluid. ALS to look for presumptive screen. Do an Acid Phosphatase presumptive test; then run P30 for confirmatory.
Vaginal Secretions
With Rape often looking for things left behind by the perpetrator.
RAPE Kit - What needs to be collected:
- Clothing from the Vicitim
- Underwear/panties - may be pubic hair or semen present
- Vaginal Swabs
- Vaginal Slides (swabs on microscopic slides)
- Blood Samples (standard to check against)
- Hair Samples - Head of Victim
- Pubic Combings (foreign hairs)
- Pubic Samples for Control Standards, pulled from pubic area; underwear on a suspect to connect back to victim.
- Nail scrapings or nail clippings.
- Other cavity swabs and slides, only if indicated.
- Pinellas will collect urine sample, to perform drug screen on the victim.
You will collect Rape Kit from the ER to provide to the Lab.
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