ScienceMakers Toolkit Manual - The History Makers

Life Science
The 4 blood types are known as A, B, AB and O. Blood type O (persons with neither A or B antigens) is the
most common in the United States (45% of the population). Type A is found in 39% of the population. Type B
is found in 12% of the population, and type AB is found in only 4% of the population.
Because of the different blood types, certain blood groups can only give or receive blood from other specifi c
blood groups.
These blood grouping systems can help police if, for example, a rare blood type is found at a crime scene and
the suspect shares that blood type. There are also distinct variations in the shape of red blood cells and other
blood components that can help link a killer to the crime. Sometimes, this evidence is enough to force a confession
or secure a conviction. Only a small sample of blood is needed, and many of these tests can even be done
on dried bloodstains.
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