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DNA Evidence Helps Solve 31-Year-Old Double Murder Case: How Does Genetic Sleuthing Work?

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A researcher uses a pipette to remove DNA from a micro test tube. DNA extraction has been a useful tool in solving crimes and clearing innocent suspects' names.  ( Maggie Bartlett/NHGRI )

A 31-year-old double murder case has been solved thanks to a new DNA research method just weeks after the Golden State Killer was finally revealed using the same technique. How does DNA evidence help in solving crimes?

Genetic Sleuthing

It has only been weeks since the Golden State Killer was identified with the help of DNA evidence, and yet another cold case has been solved with the help of genetic sleuthing. This time, authorities arrested 55-year-old William Earl Talbott II who is believed to be responsible for a 1987 double murder case.

Though investigators have long used DNA evidence to help solve crimes, what's new about these cases is that they are using a new technique called "genetic sleuthing" wherein investigators use a public genealogy database to connect distant relatives of potential suspects of a crime. Along with additional police work, the new DNA research method is said to be a valuable tool in picking out potential suspects.

In the case of Talbott, investigators found two genetic matches, both of whom at second-cousin level, suggesting that they both shared a great grandparent with the suspect. Eventually, the investigation narrowed the family tree down to Talbott's mother and father, prompting investigators to follow Talbott until they were able to gather evidence from a cup that he had thrown away.

Potential Privacy Breach?

Naturally, privacy experts worry that the method could eventually lead to privacy breaches. For one thing, innocent people might not even realize that they are under investigation because of a distant relative that they might not even know. Further, they worry that such methods could be used in investigating less serious or heinous crimes.

That said, the public's reaction to the way the method helped capture the Golden State Killer was said to be generally positive.

"We now feel that people are aware, and if they continue to participate [in GEDmatch], they're okay with that usage," said geneticist Ellen Greytak of Parabon NanoLabs, a DNA-forensics company.

Justice With The Help Of DNA

It was in the late 1980s when the federal government laid the groundwork for a national DNA database. By the early 1990s, states started to pass laws which required offenders of certain offenses to provide DNA samples. Since then, DNA evidence has helped solve a number of crimes that would otherwise be rather difficult to solve.

In most cases, DNA evidence helps the investigation in two ways. First, if a suspect has been identified, the DNA sample may be compared to evidence from the crime scene to help establish whether he or she is, indeed, involved in the crime. However, if a suspect is yet to be identified, DNA from the crime scene may be compared to the DNA database to help identify a possible suspect.

In the same way that DNA evidence can help confirm a suspect's involvement in a case, it can also help exonerate the mistakenly accused. 

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