It only requires seven or eight cells from the outermost layer of our skin.
Here’s how it works: Investigators recover cells from the scene, then use a process called polymerase chain reaction (PCR) to make lots of copies of the genes. Next, scientists mix in fluorescent compounds that attach themselves to 13 specific locations on the DNA and give a highly specific genetic portrait of that person. The whole process takes a few days, and forensic labs are often backed up analyzing data from other cases.
These 13 locations were carefully chosen because they are highly variable between people and do not give away any specific information, such as race, gender, personal health or genetic disease. The reason: authorities don’t want personal health information being used for law-enforcement purposes, such as interrogations. The chance of DNA profiles from two different people having the same genetic signature is vanishingly small.
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