Forensic serology (Chapter 8)
The function of red blood cells is to
Carry oxygen from our lungs to the rest of the body and take carbon dioxide back to our lungs to be exhausted
How do investigators find good blood spatter?
Look for spatter with directionality
Passive drops have what velocity?
Low velocity
Blood types can be
Positive or negative
What is the test to find out if there is human blood?
Precipitin Test
The study of body fluids
Serology
Blood drops form different
Shaped and sizes
What is a presumptive blood test for?
To identify the presence of drugs in the blood stream
Is it possible to destroy a DNA sample by using too much Luminol?
Yes
What helps blood to clot?
platelets
The absence of the tail indicates that the blood dropped from a ( ) degree angle. This is called a...
1.) 90 degree angle 2.) This is called a passive/ gravitational drop
The serology section of a forensic lab may deal with any or all of the following: (6)
1.) blood typing 2.) characterization of unknown blood 3.) stain patterns for crime reconstruction 4.) paternity testing 5.) semen identification in rape cases 6.) DNA techniques used for identification
Given blood spatter patterns, it is possible to determine the ( ) the blood was traveling, the ( ) , and the ( ) of the blood
1.) direction 2.) angle of impact 3.) point of origin
What are the three things that must be added to a supposed blood sample during a Kastle-Meyer test?
1.) ethyl alcohol 2.) water 3.) 3% hydrogen peroxide
What are the steps for finding and identifying blood spatter?
1.) find good blood spatter 2.) string the blood 3.) determine angle of impact
What are the 3 questions that must be answered by the forensic investigator when suspected blood stains are found at a crime scene?
1.) is it blood? 2.) is it human blood? 3.). Can it be associated with an individual?
What are the four main components of blood?
1.) plasma 2.) platelets 3.) red blood cells 4.) white blood cells
In order to determine the ( ) investigators must use a method called ( ) to find the ( )
1.) point of origin 2.) stringing 3.) area of convergence
Investigators have been using blood stain interpretation as a means to re-create crime scenes since
1939
The location of the source of blood can be determined if there are at least ( ) drops of blood spattee
2
The fastest that free-falling blood drops can travel is
25 ft/s
How many blood types are there?
4 (A, B, AB, O)
What is the Rh factor?
A blood antigen, Rh stands for Rhesus monkey, the animial in which it was first identified. Rh antigen is on the surface of RBCs when blood is Rh positive. Cells without the antigen on surface are Rh negative.
Once the AOC is determined, what can yield the point of origin?
A quick trigonometry calculation
What blood type is the universal receptor?
AB
Clumping of blood cells caused when antigens combine with antibodies
Agglutination
Blood always travels in the direction of
The applied force
Proteins that protect the body from antigens
Antibodies
Foreign substances in the bidy
Antigens
Where the strings intersect is called the
Area of convergence
What are the four presumptive blood tests to find out if there is blood?
Benzidine test Kastle-Meyer test Hemastix Luminol Test
Blood spatter analysis uses what to reconstruct the crime scene?
Blood spatter analysis uses the shapes and sizes to reconstruct the crime scene
Blood spatter, or ________________________________________, is a technique that seeks to piece together the events that caused _______________.
Blood spatter, or bloodstain pattern interpretation, is a technique that seeks to piece together the events that caused bleeding.
Which is cheaper? Blood typing to DNA profiling?
Blood typing
How can the direction of movement and speed at which the blood contacted the surface be determined?
By measuring the shape of the bloodstain on a surface
Blood typing is considered what type of evidence and why?
Class evidence because it can help narrow the suspect field, but cannot directly link to an individual person
What test is done to find out if blood can be associated with an individual?
DNA profiling
Drops form ( ) when hitting surface due to the ( ) ( ) of blood.
Drops form circles when hitting surface due to the cohesion properties of blood.
Blood typing is often used to
Eliminate suspects
Free-falling blood has a ( ) velocity, leaving ( ) drops.
Free-falling blood has a low velocity, leaving large drops.
What gives blood it's color?
Hemoglobin
What do red blood cells contain?
Hemoglobin and iron
How many velocities can there be?
High, medium, and low
____________ reacts with the ingredients in ____________ which can be made visible with a ____ __________
Iron reacts with the ingredients in Luminol which can be made visible with a UV light.
Knowing how blood got on the wall or another surface can be helpful in determining if ( ) and if the blood is ( ) in that crime.
Knowing how blood got on the wall or another surface can be helpful in deterring if a crime was committed and if the blood is evidence in that crime.
Investigators use what to calculate the height from which blood fell or the point of origin for the blood.
Law of Tangents
What blood type is the universal donor? Why?
O; there are no antigens or the Rh factor
When a wound is inflicted and blood leaves the body, a blood-spatter ( ) may be created
Pattern
how do investigators string blood?
Place strings down the long axis of the spatters
Size depends on the ( ) of blood drop
Size depends on the speed of blood drop
Blood drops fall as small as
Spheres
Serology
Term used to describe a broad range of laboratory tests using reactions of blood serum and other body fluids.
Tests for blood are so sensitive that they will expose the presence of ____________ even after a ___________ has been _________ ____________.
Tests for blood are so sensitive that they will expose the presence of blood even after a surface has been wiped clean.
The Kastle-Meyer test uses what to produce what?
The Kastle-Meyer test uses a chemical reaction between blood and hydrogen peroxide to produce a pink color.
What can help determine where a person was when they lost blood?
The angle at which a blood drop hits a surface
The ( ) the energy of the impact, the ( ) the drops are
The higher the energy of the impact, the smaller the drops are.
Directionality can be determined by analyzing what?
The tail of the bloodstain
The ( ) tells the ( )
The tail tells the tale
In the actual spatter analysis, a forensic investigator determines the ( ) of the blood
Trajectory
Blood that is many years old can still be identified as blood and analyzed for DNA. True or False.
True
How do investigators determine the point of origin?
Use a protractor to pull the strings out to the appropriate angle
How can you determine if there is blood from a crime scene?
Using tests that are portable enough to be used right at the scene.
Blood stains can be classified by their
Velocity upon impact
One of the first things that a forensic investigator needs to do when examining a blood spatter is to
Verify that the material is indeed blood
What is the trajectory of the blood?
Where it came from and how it spread over the surface
The function of white blood cells is to
defend the body against infectious organisms
