DNA: The new fingerprint

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Law enforcement uses a lot of tools to track down law breakers and one of the most telling and accurate is DNA profiling.

Also called DNA testing, DNA typing or genetic fingerprinting – DNA profiling is a technique employed by forensic scientists and law enforcement to assist in the identification of people by their unique DNA profile.

“It’s not as simple as they make it look on TV,” said Chickasaw County Coroner Andy Harmon. “But it is very effective and very accurate. It has replaced fingerprints as the way we identify people in law enforcement.”

The process begins with a sample of an individual’s DNA at a crime scene.

“We’ve been trained on how to collect these samples and how to preserve them for testing and of course maintaining a chain of evidence,” said Harmon. “People usually think of blood or semen samples that might be related to the crime, but it can also be hair, skin found under the victims fingernails or even spit on the floor.”

Harmon also pointed out that humans shed skin cells walking through a room and even sitting in a chair.

“We used to look for fingerprints so we could take a fingerprint and try to get a match,” said Harmon. “Now we look for fingerprints so we can gather those oils that make fingerprints and run a DNA profile.”

New laws require all persons convicted of a crime and sent to prison to submit a DNA profile. There is also new legislation that allows the collection of DNA material of a person is suspected of a serious crime such as rape, murder or assault.

The most desirable method of collecting a reference sample is swabbing the inside of the cheek, as this reduces the possibility of contamination and confirms the DNA donor.

Harmon said DNA obtained from decomposed bodies can identify the victim when other methods fail. Samples obtained from relatives can provide an indication of an individual’s profile, as could human remains which had been previously profiled.

“There are four criteria or fields that can match up,” said Harmon. “The more fields that match, the more certain you are of the person.”

The DNA profile is then compared against the known sample to determine whether there is a genetic match.

“CODIS (Combined DNA Index System) has become one of the biggest crime fighting tools we have,” said Harmon. “It solves a lot of crimes.”

And Harmon said DNA profiling is 99.9-percent accurate when it comes to comparing matching prints.

Harmon said the only major hitch in this process is the Mississippi Crime Lab can only process five samples at once and getting a DNA profile takes time. He said DNA profiling can be done at outside labs, but it is very expensive.

“And it still takes good police work,” said Harmon. “You can’t expect every burglary and every break-in to be solved by DNA profiling.

“You have to make the match and that means you’ve still got to develop a suspect, establish a motive and collect all the hard evidence you can to point you in the right direction,” said Harmon. “It’s just another tool in the toolbox. But it works and we use it more and more everyday.”

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