Transcript Blood

As a forensic scientist:
What forms of evidence can blood
provide?
As a forensic scientist:
What forms of evidence can blood
provide?






DNA
Blood type
Blood trails, movements
Tool marks
Toxicological Reports
Splatter marks


Directional analysis
Position of: victim, assailant, weapon
Chapter 12
Forensic Serology
Serology
 The
study of antigenantibody reactions.
History of Blood!!!



With early Transfusions
Coagulation=instant death
1901, Karl Landsteiner introduced the
typing of blood, the A-B-O system
1937, Rh Factor was introduced

Over 100 factors actually must be considered
when performing a transfusion
Structure of Blood:
1.
2.
Plasma, mostly water
Cells



Erythrocytes: (RBC)
Leukocytes: (WBC)
Platelets
Common Materials found in
the blood:






respiratory gases(O2, Co2)
Bicarbonate Ions
nutrients (amino acids,
Monosaccharides
enzymes
hormones
wastes, toxins
Blood Typing Activity
Relative Frequency of Blood
Types in Human Populations
Major components of Blood,
Plasma:



Straw colored liquid consisting mainly (90%)
of water and (7%) dissolved proteins.
Can be found outside of the circulatory
system.
Also transports:
1.
2.
3.
4.
5.
6.
Proteins: (albumin, globulins, fibrinogen)
Salts, Glucose
Amino acids
Fatty acids,
Vitamins, Hormones,
Cellular wastes
Antigens and Antibodies


Antigens: protein based structures
found on erythrocytes. Used by the
body to recognize cells as “Self” or
“NON-self” cells
Antigens can be ANY substance that
stimulates the body to produce
antibodies against it.
Antigens and Antibodies




Antibodies: a protein that destroys os
inactivates a specific antigen.
Found in blood serum/plasma
ANTISERUM: blood serum in which
there are specific antibodies
Agglutination: clumping together fo rbc
by the action of antibodies
Antigens and Antibodies
Antigens and Antibodies
Toxicology


Based on the antibody-antigen interaction,
toxins in the blood can be identified
That is how blood type was determined in
our activity
Blood Alcohol Determinations
Using the list of observable signs of intoxication
Identify this individuals level of intoxication.
ImmunoAssay techniques


assay - a quantitative or qualitative test
of a substance (especially an ore or a
drug)
to determine its components;
frequently used to test for the presence
or concentration of infectious agents or
antibodies etc.
Immunoassay techniques


Looking for Drugs, toxins, antibodies
Antibodies not found in humans are
synthesized


Usually inject compound with drug (that you
are testing for) into an animal
Why????
Animal makes antibodies because it is a
foreign substance
Immunoassay techniques

Enzyme Multiplied Immunoassay
Technique (EMIT): Detection of drugs
through a antigen-antibody reaction.

SO DETECTION occurs with any other
related forms of that drug type!!!
Immunoassay techniques
~~EMIT screening
Add subjects urine antibodies to detect
material.
 For methadone: add methadone
antibodies to the urine. [Conc] of
antibodies not used indicates
concentration used by the drug providing a
related methadone concentration

Immunoassay techniques,
~~EMIT screening

Marijuana's major active agent THC

Tetrahydrocannabinol (3- 4.5%)

Liquid Hashish oil 8-22 %
THC  Metabolized into THC-9-carboxlic acid

Is detectable


THC-9 in smokers urine is<1 mg (millionth of a
gram)
2-5 days…10 days (sometimes)
Characterization of blood stain
1.
When found at a CS, must determine



2.
3.
4.
5.
If it really is blood
Species?
How closely it can be associated with a specific
individual
Phenolphthalein: ?
Hemastix ®: ?
Luminol Reagent: ?
Precipitin Test: ?
Characterization of blood stain
1.
Phenolphthalein is used to determine
presence of blood

2.
Binds to peroxidase-like activity of
hemoglobin.
Kastle-Meyer color test

When blood, phenolphthalein and peroxide
added together a deep color will appear.
Characterization of blood stain
3. Hemastix ® is a dipstick for blood
Moisten with distilled water and dipped into
the sample
Positive presence of blood detected if stick
turns green
Characterization of blood stain
4. Luminol Reagent:
 Tests for by production of
light rather than color.
 Extremely sensitive and
can detect minute
amounts of blood
 DOES NOT interfere with
subsequent DNA analysis
Characterization of blood stain
Precipitin Test: Human Antiserum
determines if blood is from animal or human
origin.
HOW does it work?
Remember ANTIGEN-Antibody
Reaction???????
4.
Characterization of blood stain
5. Precipitin Tests: (10-15 years)
Serum for the precipitin test is obtained from rabbits which have
produced antibodies to destroy a small quantity of human
blood injected into them.
A drop of this anti-human serum is added to suspect blood, which
will precipitate its protein if it is of human origin.


Electrophoretic method: ??
Western blotting test... analysis can detect one protein
in a mixture of any number of ... Western blotting tells you
how much protein has accumulated in cells
Characterization of blood stain
5. Precipitin Tests:
Antigen
-
Antibody
+
Characterization of blood stain
Blood Splatter Lab

A: Vertical Drip Pattern
Blood Splatter Lab
Blood Splatter Lab
Categories of Bloodstains
TRANSFER
PASSIVE
PROJECTED
http://www.bloodspatter.com/BPATutorial.htm
IMPACT ANGLE DETERMINATION
ANGLE of IMPACT is the acute angle formed
between the direction of the blood drop and the
plane of the surface it strikes
Forensic characterization of semen

Acid phosphatase color test done to
determine presence of semen


Based on prostate gland secreting acid
phosphate
Use of a microscope at magnification of
400X provides ideal evidence if
spermatozoa are found

Done by immersing stain on garment into water
and then placing onto slide
Forensic characterization of semen cont.

Many people now have vasectomies or low
sperm counts



Problem solved by presence of p30 protein in
semen fluid
Antibodies to this protein made by injecting in to
other animals
Antiserum then added to suspected semen stain
Collection of Rape Evidence


Bruises and injuries usually indicate a rape
Forceful contact usually leaves a lot of evidence
behind



Hairs, semen, fiber, etc…
All outer garments form both parties should be
carefully removed over a large paper to catch any
fallen debris
Place where rape occurred should be sent to lab or
cut out piece if too big to send to lab
Collection of Rape Evidence cont.
Victim should be given a physical examination as soon
as possible

Pubic combings


Vaginal, rectal and oral swabs should be taken





Allow swab to air dry before packaging
Place another 2 smears directly on a slide
Pulled head hairs


Need 15-30
Need 50 hairs from various scalp regions
Blood sample
Fingernail scrapings
All clothing sent to lab