Blood Spatter Lesson 1

Immunoassay Techniques

When a stain is encountered at a crime scene that appears to be blood, there are several questions that must be answered:

1. Is it blood?

2. If it is blood, is it human or some other species?

3. If it is human, can it be linked to a particular individual?

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Is it Blood?

A presumptive, or screening, test for blood often used in crime scenes is the spraying of suspected areas of blood staining with Luminol. If blood was present at some point, the luminol will react with the blood stain and cause the area that was covered with blood to fluoresce. Luminol is simply a chemical reaction in which the Luminol solution reacts with iron from the hemoglobin of blood to cause a faint blue fluorescence. Even tiny amounts of iron can cause Luminol to fluoresce, so it is quite reliable in detecting trace amounts of blood. Because Luminol is extremely sensitive, it can detect even diluted samples of blood that were cleaned up long before. If luminol is sprayed in an area suspected of being a cleaned up crime scene, it will still detect blood that has been diluted up to 300,000 times. If the stain is blood, luminol will not interfere with any subsequent DNA analysis that may be done though it may destroy other components for testing within the blood.

Subject | Subject

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Is it Blood?

Another presumptive test is called the Kastle-Meyer Color Test. The Kastle-Meyer Color Test uses a solution of phenolphthalein and hydrogen peroxide on a piece of filter paper to detect blood. When blood of any quantity is present and exposed to the testing paper or solution, it will turn pink.

Subject | Subject

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Is it Blood?

Another presumptive test is called the Kastle-Meyer Color Test. The Kastle-Meyer Color Test uses a solution of phenolphthalein and hydrogen peroxide on a piece of filter paper to detect blood. When blood of any quantity is present and exposed to the testing paper or solution, it will turn pink.

Subject | Subject

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Multiple Choice

Based upon this picture, what test was done to determine whether or not a stain was blood (the picture shows a positive and negative test). 

• Kastle-Meyer presumptive blood test
• Leukomalachite green presumptive blood test
• Luminol presumptive blood test

Multiple Choice

What test is this?

• Kastle-Meyers

• Hemastix

• Luminol

• Precipitin

Multiple Choice

Luminol is a chemical used to...

• Illuminate or glow if blood is present

• Detect if the blood is from a human or not

• Determine the blood type of an individual

• Preform a White Blood Cell count

Multiple Choice

As the angle of impact gets smaller, what happens to the tail?

• Gets longer

• Gets shorter

• Stays the same

Multiple Choice

The drop shown above would have more than likely been dropped from an angle of around

• 90
• 50
• 30
• 10

Multiple Choice

As blood drops from increasing heights, what happens to the size of the blood stain?

• Gets larger.

• Gets smaller.

• Stays the same size.

Multiple Choice

What carries oxygen around the body?

• Plasma

• Red Blood Cells

• Platelets

• White Blood Cells

Multiple Choice

What is the function (job) of the platelets?

• To form clots (i.e. scabs) when you have cuts and grazes.

• To transport oxygen to the muscles

• To carry dissolved sugars.

• To produce antibodies

Multiple Choice

What is the function (job) of the white blood cells?

• To transport oxygen around the body.

• To carry dissolved sugars.

• To clot and cover wounds like cuts and grazes.

• To release antibodies to help destroy infections.

Multiple Choice

What is plasma?

• only white blood cells

• only red blood cells

• fluid part of blood

• hemoglobin

Multiple Choice

How much blood does an adult have?

• 5 liters

• 10 liters

• 8 liters

• 20 liters