Tag Archives: DNA

Who Are You? (Who, who, who, who)

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Finding DNA

 

Technicians painstakingly extract DNA from a few cells recovered from a crime scene. They duplicate segments of the DNA using the polymerase chain reaction. After analyzing the selected DNA fragments, they upload the results into the FBI’s national DNA database, the Combined DNA Index System (CODIS) Program. The result: No hits. The DNA profile is not in the database. Now what?

Researchers at Israel’s Tel-Hai Academic College may provide an answer with a DNA composite portrait based on connections between genes and external human traits.

“The new development will provide tons of leads,” research team leader Dani Bercovich told news website NoCamels.com. “We’ll know the sex of the offender and be able to estimate his height, age range, color and type of hair, eye color and ethnic background — even whether he is right or left-handed.”

Regardless of whether this technology is realized, it certainly can find a place in a mystery or crime story.

Lab Error Might Have Created False Breakthrough

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DNA molecule unwinding from a chromosome inside the nucleus of a cell. Source: National Human Genome Research Institute.

DNA molecule unwinding from a chromosome inside the nucleus of a cell. Source: National Human Genome Research Institute.

 

On July 10, 2012, The New York Times reported a match between DNA linked to the unsolved 2004 murder of Sarah Fox, a Juilliard student, and DNA recovered from a chain at the site of an Occupy Wall Street protest last March.

Protestors had wrapped the chain around an emergency exit door at a subway station to allow passengers to ride free. A surveillance video revealed people handling the chain, but they wore dark hoods and masks. To find the perpetrators, city officials decided to recover DNA from the chain. That’s when they discovered a match between DNA on the chain and DNA recovered from Sarah Fox’s CD player, which was found near her body.

The news reflects the ability of investigators to extract DNA from skin cells left on doorknobs and other surfaces. These samples are known as “touch DNA.” Recovered weapons are also swabbed for later DNA analysis.

Several surprises quickly followed the news about the DNA match. During the investigation of the 2004 murder, police and the Manhattan district attorney’s office had focused on a construction worker as the primary suspect. They never did find sufficient evidence to charge him. Now, the city reported that the matching DNA does not belong to the prime suspect.

On July 11, The New York Times announced an unexpected development: The DNA match may be due to a lab error. According to an unnamed source, the DNA recovered from skin cells on the student’s CD player and from the chain belong to a Police Department employee who works with the Office of the Chief Medical Examiner.

DNA errors wreak havoc on a criminal investigation. Mystery writers know that the same types of mistakes provide useful plot twists.

Book’em Danno . . . and Get DNA

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DNA from Arrestees

 

The FBI’s national DNA database, the Combined DNA Index System (CODIS) Program, stores DNA profiles. Leads from DNA evidence can be generated from CODIS’ Convicted Offender Index and the Forensic Index. CODIS also contains an Arrestee Index of DNA profiles of people arrested in states where local law allows the collection of samples.

Despite continuing debates about collecting DNA from arrestees, the U.S. federal government and 28 states have laws that authorize arrestee DNA collection. In their June 2012 NIJ Journal article, “Collecting DNA from Arrestees: Implementation Lessons,” Julie Samuels, Elizabeth Davies, Dwight Pope, and Ashleigh Holand explore the history and scope of this controversial practice. A copy of the article is available from the National Institute of Justice website.

By the way, the FBI imposes a requirement that states must meet before arrestee DNA profiles can be uploaded into CODIS: The FBI must approve the state’s system for expunging a DNA profile if a charge is dismissed or results in acquittal. In most states, the arrestee bears the burden for starting an expungement procedure.

Correcting Injustices with DNA

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DNA can be key to exoneration

 

The Innocence Project at Yeshiva University and other programs use DNA evidence to exonerate people wrongfully convicted of crimes. According to the Innocence Project website, the common causes of wrongful convictions include eyewitness misidentification, improper forensic science, false confessions, government misconduct, unreliable informants or snitches, and bad lawyering. Details about these causes and a geographic distribution for each cause within the United States can also be found on the website.

If DNA exoneration is a key point in your plot, you may want to peruse the U.S. Department of Justice’s report, “Post-Conviction DNA Testing and Wrongful Conviction.” It was published in June 2012, and it’s available from the National Institute of Justice website.