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