- FORENSIC CHARACTERIZATION OF BLOOD:
1)
Is it blood? Use presumptive tests:
For
VISIBLE STAINS:
Kastle-Meyer:
solution of phenolphthalein is applied to suspected blood stain, followed by
hydrogen peroxide. A bright pink color indicates the presence of blood.
Leuchomalachite
Green: same procedure as
K-M; produces blue-green color in the
presence of blood
For
INVISIBLE STAINS:
Luminol : alkaline
solution containing luminol & hydrogen peroxide is sprayed onto area. If blood is present, it will glow.Must be
viewed in darkness and photographed quickly.
2)
Is it human blood?
Precipitin Test:
Precipitin test identifies the
presence of proteins that are found only in human blood.
Precipitin Test Procedure
•
animal (usually a rat or rabbit) is injected
with human blood
•
animal’s blood forms antibodies
•
antibodies are harvested from animal’s blood
serum (“antiserum”)
•
in a test tube, an extract from the suspected
bloodstain is added to the antiserum
•
if a precipitate forms where the two meet, it is
human blood
3)
Can it be associated with an individual? DNA
- A blood type (40-42%) is most common among Caucasians and those of European descent.
- B blood type (10-12%) is most common among African Americans and Thai Asians.
- AB blood type (3-5%) is most common among Japanese & Chinese populations.
- O blood type (43-45%) is most common among indigenous peoples and Latin Americans.
- FORENSIC CHARACTERIZATION OF SEMEN
Presumptive
Tests
1. UV
light (semen fluoresces under UV light)
[What
else fluoresces? Fibers, coffee, food, detergent, most organic stains]
2.
Acid Phosphatase (reagent rapidly turns purple
if AP is present)
3.
P30 (= PSA) test (enzyme found exclusively in
seminal fluid)
Early detection methods-electrophoretic double diffusion, Ouchterlony (precipitation band)
Confirmatory
Test Required: Microscopic
examination of sperm
Most common staining method is Kernechtrot picroindigocarmine stain- Also
called Christmas Tree Stain
Seminal Fluid
• Seminal stains have to be detected in cases of rape or attempted rape, sexual murder of the female, sodomy and bestiality.
• Fertility of fluid has to be proved in disputed paternity.
• Seminal fluid choline is originated from Leyding cells.
• Smegma: If the smegma is present around glans of penis, it is suggestive of the fact that an individual did not have sexual intercourse in last 24 hours.
• Seminal stains have to be detected in cases of rape or attempted rape, sexual murder of the female, sodomy and bestiality.
• Fertility of fluid has to be proved in disputed paternity.
• Seminal fluid choline is originated from Leyding cells.
• Smegma: If the smegma is present around glans of penis, it is suggestive of the fact that an individual did not have sexual intercourse in last 24 hours.
CHEMICAL EXAMINATION
a. Florence test: (Choline Per. Iodide cystols)
• The stain is extracted
by 1% hydrochloric acid and a drop is placed on a glass slide.
• A drop of Florence
solution (Postassium iodine, iodine and water) is allowed to run under the
cover slip.
• If semen is present,
dark-brown crystals of choline iodide appear immediately.
• They are rhombic
crystals resembling haemin.
• A negative test
means the fluid is not semen.
b. Barberio’s test:
• A saturated aqueous or
alcoholic solution of picric acid* when added to spermatic fluid,
produces yellow needle shaped rhombic crystals of spermine picrate.
• In Barberio’s test, presence
of spermine in semen is detected.
• Spermine picrate
crystals are seen.
c. The Acid
phosphatase test:
• The prostatic secretion
element of seminal fluid contains a very much higher percentage of acid
phosphatase.
• This test is conclusive
in the absence of demonstrable sperms or in aspermia.
d. Creatine
phosphokinase: Level of CPK is high in seminol fluids, can be detected in
old stains of 6 months.
e. Ammouium molybdate test:
e. Ammouium molybdate test:
• For semen stains,
detect presence of phosphorous.
f. Glycoprotein P30:
This test has replaced the quantitative analysis for acid phosphatase.
g. MHS-S1 is also positive and a highly reliable test for semen.
h. Serological typing of the semen is possible by precipitin method.
g. MHS-S1 is also positive and a highly reliable test for semen.
h. Serological typing of the semen is possible by precipitin method.
- FORENSIC CHARACTERIZATION OF SALIVA
UV light
can be used to aid in locating saliva stains
- The intensity of the fluorescence can be affected by the substrate, concentration of the stain, and other body fluids
- Saliva does not fluoresce as intensely as semen
A simple test for saliva involves mixing starch,
iodine, and a sample of the presumed saliva together. Starch and iodine are a
deep blue color when mixed together. The amylase breaks down starch, however,
and the color fades (takes about 15 mins @ 37 oC).
- FORENSIC CHARACTERIZATION OF HAIR
Hair
root material-suitable for nuclear DNA analysis (Characteristic of a
particular growth phase)
If not suitable for nuclear DNA
analysis, determine if the hair is sufficient in size for mtDNA analysis (2-3cm)
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