Is luminol considered a presumptive test or a confirmatory test for blood?
Presumptive
Is luminol used for old blood or fresh blood? What do you observe when it is sprayed on that type of blood?
Old blood; when sprayed on old blood, luminol will glow.
What is the major component of plasma?
water
How many factors do we now know of in blood?
Approximately 150
Can you type old blood?
yes
What are antigens?
a toxin or other foreign substance that induces an immune response in the body; in the context of this unit, refers to the proteins found on the cellular membrane of red blood cells that will provoke an immune response in people who do not have that type
Wipe pattern
a bloodstain pattern created when an object moves through an existing stain, removing it or changing its appearance
Void
an absence of stains in an otherwise continuous bloodstain pattern
Target
surface onto which blood is deposited
Transfer or contact pattern
A bloodstain pattern created when a wet, bloody surface comes in contact with a second surface. A recognizable image of all or a portion of the original surface may be observed in the pattern.
What is the most common type of blood found in the US?
O
Swipe pattern
transfer of blood from a moving source onto an unstained surface
Does blood typing have probative value? Why or why not?
Yes. Although it is class evidence rather than individual evidence, it can create a limited association between a suspect and crime scene or it can also exclude a suspect.
Satellite spatter
small droplets of blood distributed around a drop or pool of blood as a result of the blood hitting a surface
What type of blood cells are used in the DNA typing of blood?
white
Spine
pointed or elongated stains that radiation from the central area of a bloodstain
Point of origin
common area in a three-dimensional space to which the trajectories of several blood drops can be retraced
What type of blood cells produce antibodies?
white
In normal human blood, what type of blood cell is the most numerous?
RBCs
What shape does a blood droplet remain in space until it comes in contact with a surface?
spherical
What effect does the softness or hardness of a target surface have on a falling blood droplet?
The softer the target surface, the more a blood droplet will break apart.
Passive drop (bleeding)
bloodstain formed by the force of gravity acting alone
If a blood drop falls on carpet, can the direction of the blood be determined?
yes
Point of convergence
common area on a two-dimensional surface over which the directionality of several blood drops can be retraced
Parent drop
the original blood droplet that casts off a wave or satellite
Low velocity impact
spatter that produces the largest blood droplets
Medium velocity impact
spatter that produces intermediate sized blood droplets
Can blood spatter evidence be presented in court?
yes
Is blood typing considered a class or individual characteristic?
class
Impact site
the point where force meets a blood space
How can investigators individualize blood evidence?
Comparing DNA
Flow pattern
a change in the shape and direction of a blood stain due to the influence of gravity or movement of the object
What tests might an investigator use to determine whether or not a suspect stain is blood?
Only comfirmatory tests are microscopic (look for blood cells) and Kastle-Meyer test
High velocity impact
spatter that produces the smallest blood droplets
What CAN a precipitin test be used to identify?
The species of animal the blood came from. Each species has its own precipitin test. A positive on that precipitin test would indicate that the blood came from an animal of that specific species. A negative would indicate that it came from an individual o
What standard test would an investigator use to determine whether a blood stain was human or animal blood?
Precipitin test
Flight path
path of a blood drop as it moves through space
Expirated blood
blood that is blown out of the nose, mouth, or wound as a result of air pressure
List all presumptive tests for blood (4).
hematest, leucomalachite, luminol, Takayama and Teichmann
Who is the person responsible for the ABO classification system?
Landsteiner
Directionality
of or indicating direction
If a person's blood has the Rh factor, the blood is said to be Rh ________
positive
What percentage of the population is a secretor?
80%
Cast-off pattern
pattern created when blood is released or thrown from a moving blood-bearing object
What is the relationship between a person's blood type, and the presence of specific antigens and antibodies?
Type A blood has A antigens and B antibodies.
Type B blood has B antigens and A antibodies.
Type AB blood has both A and B antigens and no antibodies at all.
Type O has no antigens at all and contains both A and B antibodies.
What is a secretor?
Someone whose antigens are found in bodily fluids other than blood
Back spatter
blood directed back toward the source of energy or force that caused the spatter
BSA
a field of forensic science that deals with the properties of blood and the patterns produced under different conditions
Angle of impact
the acute angle formed between the direction of a blood drop and the plane of the surface it strikes
If a person has no A or B antigens, what is his or her blood type?
Type O
Which blood type is known as the universal donor, and why?
Type O. Since it contains no A or B antigens, it will not provoke an immune response from any type of blood it is added to.
If a person has no A or B antibodies, what is his or her blood type?
Type AB
Which blood type is known as the universal receiver, and why?
Type AB. Since it contains neither type of antibodies, it will not produce an immune response when exposed to any type of blood regardless of which type of antigens the other blood contains.
What is the formula for determining angle of impact?
arc sine (width/length)
What is the study of bodily fluids called?
serology
What is the clumping of red blood cells called?
agglutination
What are the common names for erythrocytes, leukocytes, and thrombocytes?
Erythrocytes = red blood cells, Leukocytes = white blood cells, Thrombocytes = platelets
What is the name of the oxygen molecule that gives red blood cells their color?
hemoglobin
A blood droplet is perfectly round. What was its angle of impact?
90 degrees
How can you determine the direction of blood travel?
The shape of the blood drop
What is the liquid portion of the blood called?
Plasma
What type of spatter would a gunshot wound close to the head produce?
High velocity spatter
At what angle of impact does a "tail" begin to form on a blood stain?
30 degrees
If type A blood is found in approximately 35% of the population and PGM 2-1 enzyme is found in approximately 12% of the population, what percentage of the population will have type A, PGM 2-1?
4.2% = (.35
.12)
100
Acid phosphatase is a major constituent of _____________________.
semen
Who is the person who first used the precipitin test to solve a case? (Hint: answer is in a case study).
Uhlenhuth
The presence or absence of how many antigens determines an individual's blood type in the ABO system?
2
Which substance turns green in the presence of blood?
leucomalachite