DNA PROFILING AND THE LAW

Since 1994, the federal government has been collecting DNA profiles of offenders in the Combined DNA Index System (CODIS), a computer database that contains more than 10 million profiles from criminals convicted of specific crimes in all 50 states. Each profile consists of a banding pattern that represents 15 specific STR regions scattered throughout our genomes. Forensic scientists typically describe the likelihood that any two unrelated people will have the same number of repeated sequences at all 15 regions as 1 in some number of quintillions (billions of billions) (INFOGRAPHIC 7.7).

INFOGRAPHIC 7.7 DNA PROFILING USES MANY DIFFERENT STRs
To create a DNA profile, scientists analyze 15 different STRs (yellow boxes) scattered among our chromosomes. Sharing the same number of repeats at any particular STR is relatively common—typically 5% to 20% of people share the same pattern at any one STR site. But it is the combined pattern of STR repeats at multiple sites that is unique to a person; the more STRs tested, the more discriminating the test becomes.

So far, the database of DNA profiles has proved helpful in more than 190,000 cases. More significantly, DNA evidence is helping to change the criminal justice system for the better. That more than 300 prisoners have already been exonerated by the Innocence Project suggests that many more may have been wrongly convicted but lack the evidence to support their cases. In the majority of criminal cases, there is no DNA evidence.

Roy Brown with his family upon his release from prison.

“How many more wrongful convictions will it take for New York to begin addressing the systemic problems that lead to such miscarriages of justice?” asked Neufeld in 2007, when Brown’s case was being reviewed.

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Recognizing the flaws in our criminal justice system, Innocence Project lawyers are working with several states to change the way law enforcement operates. For example, studies have shown that witnesses more accurately identify perpetrators if they are shown suspects one at a time instead of in a group line-up. Project lawyers are also helping to force changes in the way interrogations are conducted, calling for them to be videotaped to reduce the possibility of forced confessions. In addition, they are lobbying for legislation to ensure that evidence from crime scenes is properly collected and maintained, since DNA evidence can be ruined or contaminated during collection. They also advocate that anyone convicted of a crime be able to gain access to DNA testing.

“The key is that DNA really gives us an opportunity to start making the other institutions in the system more scientific and reliable as well,” says Neufeld.