Forensic ScienceThe Basics of Blood Typing and Spatters

What makes up our blood?• RED BLOOD CELLS (Erythrocytes) – The most abundant

cells in our blood; they are produced in the bone marrow and contain a protein called hemoglobin that carries oxygen to our cells.

• WHITE BLOOD CELLS (Leukocytes) – They are part of the immune system and destroy infectious agents called pathogens.

• PLASMA – This is the yellowish liquid portion of blood that contains electrolytes, nutrients and vitamins, hormones, clotting factors, and proteins such as antibodies to fight infection.

• PLATELETS (Thrombocytes) – The clotting factors that are carried in the plasma; they clot together in a process called coagulation to seal a wound and prevent a loss of blood.

Blood Facts

The average adult has about FIVE liters of blood inside of their body, which makes up 7-8% of their body weight.

Blood is living tissue that carries oxygen and nutrients to all parts of the body, and carries carbon dioxide and other waste products back to the lungs, kidneys and liver for disposal. It also fights against infection and helps heal wounds, so we can stay healthy.

There are about one billion red blood cells in two to three drops of blood. For every 600 red blood cells, there are about 40 platelets and one white cell.

http://www.bloodbankofalaska.org/about_blood/index.html

Genetics of Blood Types

• Your blood type is established before you are BORN, by specific GENES inherited from your parents.

• You inherit one gene from your MOTHER and one from your FATHER.

• These genes determine your blood type by causing proteins called AGGLUTINOGENS to exist on the surface of all of your red blood cells.

What are blood types?

http://learn.genetics.utah.edu/units/basics/blood/types.cfm

There are 3 alleles or genes for blood type: A, B, & O. Since we have 2 genes, there are 6 possible combinations.

Blood Types

AA or AO = Type ABB or BO = Type B

OO = Type OAB = Type AB

How common is your blood type?

46.1%

38.8%

11.1%

3.9%

Blood Transfusions

A blood transfusion is a procedure in which blood is given to a patient through an intravenous (IV) line in one of the blood vessels. Blood transfusions are done to replace blood lost during surgery or a serious injury. A transfusion also may be done if a person’s body can't make blood properly because of an illness.

Who can give you blood?

People with TYPE O blood are called Universal Donors, because they can give blood to any blood type.

People with TYPE AB blood are called Universal Recipients, because they can receive any blood type.

Rh + Can receive + or - Rh - Can only receive -

Universal Donor

Universal Recipient

Rh Factors• Scientists sometimes study Rhesus monkeys

to learn more about the human anatomy because there are certain similarities between the two species. While studying Rhesus monkeys, a certain blood protein was discovered. This protein is also present in the blood of some people. Other people, however, do not have the protein.

• The presence of the protein, or lack of it, is referred to as the Rh (for Rhesus) factor.

• If your blood does contain the protein, your blood is said to be Rh positive (Rh+). If your blood does not contain the protein, your blood is said to be Rh negative (Rh-).

A+ A-B+ B-

AB+ AB-O+ O-

http://www.fi.edu/biosci/blood/rh.html

Blood Evidence• Blood samples – Can be analyzed to determine blood

type and DNA, which can be matched to possible suspects.

• Blood droplets – Can be analyzed to give clues to the location of a crime, movement of a victim, and type of weapon.

• Blood spatter – Can be analyzed to determine patterns that give investigators clues to how a crime might have happened.

Microscopic Views

Bird Blood

Cat Blood

Dog Blood

Fish Blood

Frog Blood

Snake BloodHuman Blood

Horse Blood

What does the abbreviation BPA represent? Bloodstain Pattern Analysis

What can an investigator learn from the analysis of a blood spatter? Type and velocity of weapon Number of blows Handedness of assailant (right or left-handed) Position and movements of the victim and assailant during and after the attack Which wounds were inflicted first Type of injuries How long ago the crime was committed Whether death was immediate or delayed

How does a blood droplet

form? Click the image

for an animation.

Source: http://science.howstuffworks.com/bloodstain-pattern-analysis1.htm

Light SourceInvestigators will first examine the crime scene to look for areas that may contain blood. They may use a high-intensity light or UV lights to help them find traces of blood as well as other bodily fluids that are not visible under normal lighting conditions.

How is blood evidence detected at a crime scene?

Blood Reagent TestsThese tests, referred to as presumptive tests, are used to detect blood at crime scenes based upon the properties of hemoglobin in the blood. Further tests at the crime lab can determine if it is human blood or not.

Examples:

• Phenolphthalein is a chemical that is still utilized today and is usually referred to as the Kastle-Meyer test and produces a pink color when it reacts with hemoglobin.

• HemaStix is a strip that has been coated with tetramethylbenzidine (TMB) and will produce a green or blue-green color with the presence of hemoglobin.

Kastle-Meyer TestVideo

HemaStix

Luminol This chemical is used by crime scene investigators to locate traces of blood, even if it has been cleaned or removed. Investigators spray a luminol solution is throughout the area under investigation and look for reactions with the iron present in blood, which causes a blue luminescence. One problem is that other substances also react, such as some metals, paints, cleaning products, and plant materials. Another problem is that the chemical reaction can destroy other evidence in the crime scene.

Luminol Reaction

LCV or Leuco Crystal Violet, is one type of chemical process that is used for blood enhancement. Using this test helps to make the blood evidence more visible so it can be photographed and analyzed.

FluoresceinThis chemical is also capable of detecting latent or old blood, similar to luminol. It is ideal for fine stains or smears found throughout a crime scene. After the solution has been sprayed onto the substance or area suspected to contain blood, a UV light and goggles are used to detect any illuminated areas, which appear greenish-white if blood is present. It may also react to many of the same things as luminol (copper and bleach).

Fluorescein Reaction in

UV Light

Bloodstain Pattern Analysis Terms

• Spatter – Bloodstains created from the application of force to the area where the blood originated.

• Origin/Source – The place from where the blood spatter came from or originated.

• Angle of Impact – The angle at which a blood droplet strikes a surface.

Parent Drop

Spines

Satellite Spatters• Parent Drop – The droplet from which a

satellite spatter originates.• Satellite Spatters – Small drops of blood

that break of from the parent spatter when the blood droplet hits a surface.

• Spines – The pointed edges of a stain that radiate out from the spatter; can help determine the direction from which the blood traveled.

• Passive Bloodstains– Patterns created from the force of gravity– Drop, series of drops, flow patterns, blood pools, etc.

• Projected Bloodstains– Patterns that occur when a force is applied to the

source of the blood– Includes low, medium, or high impact spatters, cast-

off, arterial spurting, expiratory blood blown out of the nose, mouth, or wound.

• Transfer or Contact Bloodstains– These patterns are created when a wet, bloody object

comes in contact with a target surface; may be used to identify an object or body part.

– A wipe pattern is created from an object moving through a bloodstain, while a swipe pattern is created from an object leaving a bloodstain.

Images from http://www.bloodspatter.com/BPATutorial.htm

Blood Spatter Movie

Types of Bloodstain Patterns

Blood Spatter Labs

• You will be creating sample drop patterns using single drops and multiple drops. We will also investigate the effect of motion and the angle of impact on blood spatter.

• This can be messy! Be very careful to keep the blood on the paper and not on yourself, the table, or floor.

• Hold you hand as steady as possible when making the drops. Brace your wrist against the meter stick to help you.

• Get your materials from your teacher – paper, black marker, meter stick, goggles, and a bottle of blood.

If you make a mess, clean it up immediately!

Lab 1: Single Droplets

25 50

Single Drops Group Members

75 100

Single Drops Group Members

• Label two large pieces of construction paper as shown below.

• To do the lab, put on your goggles and hold the dropper bottle upside down so that the end of it is 25 cm from the paper. GENTLY squeeze the bottle so that ONE drop of blood is released and lands in the correct location on your paper. It should NOT hit the meterstick.

• Repeat TWO more times at this height for a total of three drops.

• Continue making drops of blood on your paper, but put the drop in a different area of the paper and change the height each time.

• When you are done, analyze your results and answer the questions on your worksheet.

Make a mistake? Use a paper towel to wipe it off your paper!

Keep your drops in the correct area of the paper.

Use your results to answer these questions.

What did you notice about the diameter of the parent droplets as you increased the height of the drop?   

 How do the spines compare from the different heights?   

Lab 1 Questions

Lab 2: Multiple Droplets• Label a long piece of butcher paper (2 -3 meters in length) as shown below.

• To do the lab, put on your goggles and hold the dropper bottle upside down so that the end of it is 25 cm from the paper. GENTLY squeeze the bottle so that ONE drop of blood is released and lands in the correct location on your paper. The drop should NOT hit the meterstick.

• Without moving your hand, release ONE more drop onto the first drop at that height. If you make a mistake, wipe it off with a paper towel and try it again.

• Continue making drops of blood on your paper so you have three sets for each height.

• When you are done, analyze your results and answer the questions on your worksheet. Clean up your area and put away your materials before you leave class.

Multiple Drops Group Members

25 50 75 100

Keep your drops in the correct area of the paper.

Use your results to answer these questions.

What happened when one drop landed on top of another one?   

 What did you notice about the diameter of the parent droplets as you increased the height of the drop?    

What do you notice about the diameter of the satellite spatter as you increased the height of the drop?

Lab 2 Questions

Lab 3: Motion Droplets• During this lab, you will see how motion affects the size and shape of the

droplets and spines. You will need a long piece of butcher paper (4-5 meters in length) and tape to secure it to the floor. You will also need safety goggles.

• To do the lab, you will need to hold the dropper bottle upside down so that your hand is out and away from your body (waist level), but is still over the paper.

• Start off walking at a SLOW WALKING RATE along the paper strip from one end to the other and GENTLY squeeze the bottle as you walk so that blood is released ONE DROP at a time. Be sure that all the drops land on your paper strip.

• Repeat this procedure using a NORMAL WALKING RATE and a FAST WALKING RATE.

Walking Direction

• When you are done, analyze your results and answer the questions on your worksheet. Clean up your area and put away your materials before you leave class.

Miss the paper? Use a paper towel to wipe it off the floor!

Use your results to answer these questions.

Draw a sketch of the droplets showing the size, shape, and/or distance between them at each speed in the chart below.

 

What did you notice about the shape of the droplets as you increased your walking speed?   What did you notice about the spines as you increased your walking speed?   What did you notice about the distance between the droplets as you increased your walking speed?

Lab 3 Questions

• You will be creating sample drop patterns created by droplets landing at different angles from the same height.

• Label five pieces of copy paper with your names and then indicate the angle for each droplet - 15o, 30o, 45o, 60o, or 75o.

• Place the first piece of paper on the clip board and align the clipboard with the 15o line. Hold the bottle of blood at a height of 50 centimeters from the top of the table.

• GENTLY squeeze the bottle so that ONE drop of blood is released and lands on the paper. Repeat two more times at this angle.

• Continue testing by dropping blood from a height of 50 centimeters at each of the other angles.

Lab 4: Angle of Impact

• When you are done, answer the questions on your worksheet. Clean up your area and put away your materials before you leave class.

Angle

Guide

Clipboard & Paper

Height of50 cm

Use your results to answer the question.

What did you notice about the shape of the droplets as you increased the angle of the paper?

Lab 4 Questions

Which of the three blood droplets shown would have been created by a wound in the lower part of the leg? Explain.

If you find a trail of blood with droplets that are round and close together, what could this mean?

If you have a blood droplet as shown at left, what does it tell you? Explain.