The technology that cleared JonBenet Ramsey's family of her murder can detect the slightest bit of genetic material. Husband and wife forensic experts Max and Lucy Houck explain:
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What is touch DNA?
The technique has dramatically increased the number of items of evidence that can be used for DNA detection. In the 1980s, in order to perform DNA analysis on a crime scene or victim, forensic investigators needed a blood or semen stain about the size of a quarter. The sample size fell in the 1990s to the size of a dime and then became: “If you can see it, you can analyze it.”
Touch DNA doesn’t require you to see anything, or any blood or semen at all. 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.