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All About Blood
Human blood, which makes up about 7 percent of a person’s body
weight, is 78 percent water. The solids in the blood make it a useful
substance, obviously required for life. Without blood, the cells of
the body would suffocate and die in their own waste products. This
is because blood transports oxygen to the cells and removes car-
bon dioxide from them. In addition, blood carries nutrients like pro-
teins and carbohydrates to the cells. Each circuit of blood around
the body passes through the lungs, kidneys, and liver, where the
majority of the transfers of nutrients and waste products occurs.
Without this transfer, people could not survive.
the crime. The chemical properties of blood are an important part of the
reason why it spatters as it does, but they also provide critical information
for determining whether a sample really is a useful specimen of human
blood. Taking the time to check the chemical properties is a very important
step in blood analysis.
After screening the blood sample to determine that it is important to the
case, the real examination of the blood can begin. Often, the samples are sent
to two or three different departments of the central crime laboratory. Blood is a
good source of DNA, a powerful piece of evidence when establishing identity.
Most blood is also tested to determine the blood type of the subject who lost it.
The forensic physicist is not concerned with the DNA or blood type, though.
She wants to see the way the blood was found because the patterns of droplets
or spray can tell her a detailed story about what happened there.
Because blood is so thick, it does not flow as quickly down a surface
as other fluids might. In addition, it tends to react in specific ways when
