forensic serology

Question 1

serology

Answer 1

study of bodily fluids (blood, semen, saliva) left at the crime scene
finding DNA on an item of evidence does not necessarily provide the source of the DNA
serology is quick and easy way to ID body fluids
preliminary test to DNA
fast, efficient, inexpensive
saves time and effort
identifies biological stains, avoids needless DNA on non-biological stains

Question 2

forensic analysis of blood

Answer 2

visual examination of evidence
presumptive screening (is it blood?)
confirmatory testing (is it for sure blood?)
species determination (is it human blood?)
identification (whose blood is it?)

Question 3

presumptive screening

Answer 3

highly sensitive
not specific

Question 4

confirmatory test

Answer 4

presumptively positive tests can be more specifically tested
tests positive for the substance in question and only that substance
lacks sensitivity
relatively large amount of the substance must be abaikable
tested in the laboratory rather than the field
controlled conditions
additional equipment

Question 5

presumptive/confirmatory procedure

Answer 5

allows sorting of potential evidence into processing categories
test for DNA
no DNA testing
helps decide what is relevant and what is not

Question 6

blood

Answer 6

by definition is a tissue
circulates throughout the body
supplies nutrients and oxygen
removes waste
helps regulate body temp, fluids, salt balance, etc
defense against invading organisms- part of the immune system

Question 7

blood components

Answer 7

solid elements (red blood cells, white blood cells, platelets)
liquid (55%): plasma, serum

Question 8

red blood cells (erythrocytes)

Answer 8

produced in bone marrow
have no nucleus, not useful for DNA analysis
6-8 um in size, disk shaped cells
most abundant cells in the blood about 99%
principal carriers of hemoglobin
short life span ~4 months
antigens on the cell surface (ABO) for blood typing

Question 9

hemoglobin

Answer 9

transports oxygen and carbon dioxide throughout the body’s circulatory system
red colored molecule
binds ~97% all oxygen in body
heme portion is target for blood presumptive test

Question 10

white blood cells (leukocytes)

Answer 10

produced in bone marrow
have a nucleus, useful for DNA analysis
vital source of defense against external organisms
white blood cells also clean up dead cells and tissue debris that would otherwise accumulate and lead to problems

Question 11

platelets (thrombocytes)

Answer 11

produced in bone marrow
contain no nuclei
irregularly shaped colorless bodies
participate in blood clotting process to stop bleeding (hemostasis)
only active when damage occurs to the circulatory system walls

Question 12

liquid blood plasma

Answer 12

mainly water
clear liquid suspends the solid elements
contains soluble proteins such as albumins, globulins, fibrinogen

Question 13

serum

Answer 13

fluid separates from blood or plasma when the blood clots
plasma without the clotting factors
used in species testing

Question 14

presumptive blood tests, chemical tests

Answer 14

kastle-meyer phenolphthalein test (pink)
leucomalachite green (LMG) color test (green)
luminol
based on the fact that hemoglobin (and some of its derivatives, heme) exhibit a peroxidase activity
oxidant (hydrogen peroxide) oxidizes a colorless reagent to a colored reagent
heme catalyzes this oxidation by cleaving an oxygen from H2O2
phenolphthalin to phenolphthalein

Question 15

phenolphthalein test

Answer 15

very sensitive (1:10,000 to 1:100,000 (non-visible))
phenolphthalein reagent, 3% H2O2
positive control is 1:10 pigs blood
negative control is water + reagents

Question 16

phenolphthalein test procedure

Answer 16

test reagent on positive and negative controls
sample questioned stain
indirect testing is transfer small portion of stain onto moistened swab or piece of filter paper
direct testing is tease fibers or take a small cutting of the stain
perform a general swabbing when no stains are observed.
use a slightly moistened swab to test zones or sections of an item, perform an indirect test on the swab
step 1: add 1-2 drops phenolphthalein reagent, should be no color development at this point, rules out false positives due to presence of chemical oxidants such as rust
step 2: add 1-2 drops 3% H2O2, positive if immediate pink color development, negative if no color change
swab will eventually turn pink even if negative over time due to the nature of oxidation reactions

Question 17

specificity of phenolphthalein test

Answer 17

can weed out false positives between steps 1 and 2
will not detect differences in animal or human blood
chemical oxidants

Question 18

stability of phenolphthalein test

Answer 18

relatively stable if the reagents are stored separately and refridgerated
amber bottle light affects stability
zinc pellets, bind free oxygen and prevents oxidation

Question 19

luminol

Answer 19

chemical combined with oxidant and sprayed over area
emits a blue-white glow (must have darkness)
only visible for short time ~30 sec
can spray again, but dilutes sample even more
must have qualified photographer available
every sensitive to hemoglobin (1:5,000,000 dilution)
used to detect clean up

Question 20

blood confirmatory testing

Answer 20

microcrystalline tests
techmann and takayama tests
based on the formation of distinctive hematin and hemochromogen crystals that form when a chemical solution is added and heated
viewed under a microscope
crystal tests require a larger sample than presumptive tests
easy to over/under heat crystal preparations, resulting in no crystal formation, even when known blood is present
false negative

Question 21

blood confirmatory testing

Answer 21

microcrystalline tests
techmann and takayama tests
based on the formation of distinctive hematin and hemochromogen crystals that form when a chemical solution is added and heated
viewed under a microscope
crystal tests require a larger sample than presumptive tests
easy to over/under heat crystal preparations, resulting in no crystal formation, even when known blood is present
false negatives

Question 22

species origin

Answer 22

diffusion reactions and electrophoretic methods
ouchterlony test

Question 23

ouchterlony test

Answer 23

based on antibody antigen reaction between human blood and human antiserum
antigen - serum protein
antibody - produced when foreign serum protein is detected
antibody will only attach to one species’ protein
gel plated created to receive serum and anti-serum
anti-serum is placed in center
knowns and unknown (evidence) placed in surrounding
precipitate lines form where reaction occurs

Question 24

semen

Answer 24

fluid of complex composition, produced by male sex organs
spermatozoa is the cellular component
seminal composition
avg ejaculate is 3.5 mL (range is 2-6mL)
average of over 100 million sperm / mL of semen (range of 50-150 million/mL)

Question 25

forensic analysis of semen

Answer 25

using the naked eye (ambient light) dried semen stains are often off-white to faint yellow in color semen stains floresce under alternate light sources (ALS) visualized using 400-500nm wavelength with yellow/orange goggles common practice to visually access items of evidence under alternate light sources to locate possible semen stains

Question 26

acid phosphatase (AP)

Answer 26

enzyme secreted from the prostate gland high concentrations of AP in semen not specific to human semen-high AP in primate semen can also be detected in vaginal secretions degrades at a much faster rate than sperm cells water soluble negative result with presumptive AP test does not necessarily mean semen is not present may continue on with microscopic examination on items that have negative AP test results

Question 27

AP presumptive test

Answer 27

test reagent on positive and negative controls swab questioned evidence stain moisten swab with water swab outer edges of stain on cloth because AP is water soluble and diffuses to edges of stain spermatozoa are most likely to stay put in middle of the stain add one drop of AP reagent positive if purple in one minute negative if no color change, pink color change, or color change after one minute degraded or dilute AP may result in faint purple or pink color development or late color development false positives in vaginal acid phosphatase, fecal material, plant matter (cauliflower), spermicides, some feminine hygiene products AP reagent - one components are mixed together, reagent is not as stable as when stored separately store in amber bottle or freeze aliquots use reagent before it begins to darken past straw color (test controls)

Question 28

semen confirmatory testing

Answer 28

presence of intact spermatozoa in a biological stain lack of sperm does not necessarily mean that the stain isn't semen, just that sperm are not present oligospermia=deficienct in the number of sperm in semen azoospermia = no sperm in semen vasectomy = surgical procedure for male sterilization in which the vas deferent are severed and then sealed in a manner such to prevent sperm from entering into the seminal stream christmas tree staining and phase shift staining other microorganisms and cells may resemble spermatozoa yeast, protozoans, white blood cells, free nuclei these can be differentiated from human sperm based on cell morphology) staining, tail, if attached, size

Question 29

parts of semen

Answer 29

head oval or pear shaped with acrosomal cap (aids sperm entry to egg) house nuclear material (DNA) about 4.5 um -2.5 um wide midpiece houses mitochondria, energy for sperm cell tail used for mobility, made of protein, long and fragile (first part to breakdown and easily detached) about 40 um long

Question 30

christmas tree stain

Answer 30

differential staining of head acrosomal cap does not pick up stain as well and appears translucent / faintly stained remainder of head stains red tail if present stains green/blue

Question 31

phase shift staining

Answer 31

acrosomal cap appears dark head appears light

Question 32

saliva

Answer 32

evidenced in bite marks, licked adhesives, eating/drinking surfaces main component is amylase (can test for) amylase exists in many other body fluids, serum (blood), urine, sweat, lip mucuous, semen, feces occurs in higher amounts in saliva

Question 33

forensic analysis of saliva

Answer 33

amylase diffusion on a gel plate develop with iodine, any amylase will break down starch on gel plate and create a clear circle measure and record results