Blood Anatomy

Forensics, 4th hour

Blood

Blood is a human tissue. Tissues consist of different types of cells working together. Forensic blood evidence consists primarily of blood types and blood spatter patterns.

Parts of Blood

There are 4 types of blood. The top layer is called Plasma, the middle layer is the Buffy Coat which consists of the White Blood Cells and the Platelets, and the bottom layer consists of the Red Blood Cells.


Plasma

The Plasma is the liquid part of blood that carries nutrients and hormones throughout the body. The Plasma makes up about 55% of blood tissue. Plasma should not be confused with Serum. When blood clots, the solid clot separates from the liquid components. This liquid part of clotted blood is called Serum.







RBC, Platelets, WBC

RBC is far right, Platelets surround red blood cells in center photo, WBC Left

Presumptive Blood Tests

One of the jobs of a forensic scientist is to determine if a substance is blood. Kastle was the first to develope a presumptive blood test in 1903.

Phenolphthalein Test

The Phenolphthalein Test is also known as the Kastle Meyer Test. A positive test produces a pink color. However, it can produce false positives in the presence of many body fluids including saliva or pus as well as other non human substances.

Luminol Test

The Luminol Test uses UV light to cause blood to glow blue when sprayed with Luminol. Interestingly, this blood test works best with older blood. The older the blood the more it glows. Luminol can also give false positive results in the presence of many heavy metals.

Other Confirmatory Tests

Many of these tests also do not rule out the possibility of another animal's blood as a source. There are other chemicals that can be used to confirm if the blood is from human or another animal.

This is Blood Anatomy

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