Serology Flashcards
Serology is the study of
body fluids and stains at a crime scene
plasma
fluid portion of blood
erythrocytes
red blood cells, they transport oxygen and carbon dioxide to and from cells
leukocytes
white blood cells, protects body from foreign substances
thrombocytes
responsible for blood clotting, platelets
serum
fluid remains after blood clotted
In 1901
Karl Landsteiner discovered all human blood wasn’t exactly the same
for every antigen
there is a specific antibody
antibodies
proteins found in plasma/ serum that neutralizes specific antigens
antiserum
serum containing one type of antibody
antiserum: when complementary antibodies attach to
antigens, they create networks of linked cells, appear clumping (agglutination) not clotting
more than __
15 blood antigen systems
Characterizing Blood: preliminary color test
First step, reacts with hemoglobin
Characterizing Blood: preliminary color test- Kastle-Meyer test
Second Step, produces a bright pink
Characterizing Blood: preliminary color test- Hemastix strips
produces green
Characterizing Blood: Luminol produces
light when reacting with the iron in hemoglobin, even dilute traces of blood
Characterizing Blood: Microscopic Examination
Third Step, used to look for real blood cells
In order to tell if the blood is human: precipitin test and then
uses antiserum to test for human blood proteins
After, microscopic examination can identify differences in red blood cells
parents transmit information about traits to their offspring using
gametes or sex cells (females- egg cells [ovum] male- spirm cells)
each individual has
2 genes for each trait
if 2 genes you inherit are same
homozygous
if 2 genes you inherit are different
heterozygous
different forms of a gene are
alleles
genotype
individuals genes (alleles)
physical appearance results from
alleles is phenotype
not all alleles
get expressed
A Type
I^A I^A or I^Ai
B Type
I^B I^B or I^Bi
AB Type
I^A I^B
O Type
ii
bloodstain patterns
can provide the “what, when, how” of a crime and allows reconstruction of events
What can be learned through bloodstains? Origins of Blood
Approx. distance between source and target surface
estimated time that has elapsed
What can be learned through bloodstains? Type and Direction of Impact
approx. speed of droplets impact
approx. direction the blood droplets where traveling when they impacted the surface
direction in which a weapon may be swinging
What can be learned through bloodstains? position of victim or perpetrator
position of victim or suspect
What can be learned through bloodstains? Movement and direction after initial assault
direction where blood trailed after impact
whether blood was wiped or smeared
movement of an individual between focal points (walking, running while bleeding)
3 categories of blood
passive blood patterns
projected blood patterns
transfer/contact blood patterns
3 categories of blood; passive blood patterns
created with the force of gravity
dripping blood viscosity 4x thicker than water
drip stain will not change size after reaching terminal
3 categories of blood; projected blood patterns
occurs when a force is applied
low-velocity- impact splatters, dripping, 4mm or more diameter
medium-velocity- weapon cast off, repetitive drop, explosives
high velocity- gun shot, explosives, droplets are highly scattered and less than 2mm
3 categories of blood; transfer/contact blood patterns
created when a bloody object contacts a large surface
gives clues about type and/or movement of an object
wipe/smudge- when a clean object moves through wet blood
swipe/smear- when bloody object moves across a clean surface
collection- liquid blood; pools and drops
try to collect before coagulation
suck it up with a syringe or pipette
cotton swab or gauze
collection- liquid blood; drawn blood from a living person
one tube with EDTA (anticoagulant)
one tube without
refrigerate
Collection-bloodstains
wet items are air dried then put into paper containers
dry stains that can be brought to lab, scrape onto paper and transfer to moistened cotton/ gauze
bodily fluids
sweat, saliva, tears, urine, vaginal secretions
all of these can be useful if they contain enough cells to produce a DNA sample or for detection of drugs and can be used to reconstruct events
