NEW YORK — Advances in DNA testing have contributed to more than 600 exonerations in the United States since 1989, according to the Innocence Project, even as structural barriers continue to limit access to post-conviction analysis.
At the same time, the organization reports that restrictive legislation and the high cost of testing remain significant obstacles to broader use of DNA evidence in criminal cases.
The development of DNA testing began in 1986 in the United Kingdom, when geneticist Alex Jeffreys used DNA profiling to assist in the investigation of the murders of Lynda Mann and Dawn Ashworth. As reported by A&E, the technique was used to screen thousands of men and ultimately identify the perpetrator.
By 1988, DNA testing had been introduced in the United States, where it played a key role in the conviction of Tommie Lee Andrews, the first individual in the country convicted using DNA evidence.
Since then, technological developments have expanded the capabilities of DNA analysis. Early methods required relatively large samples, but by the late 1990s, forensic scientists were able to generate accurate DNA profiles from much smaller traces, according to A&E.
The Innocence Project explains that DNA can be collected from a range of sources, including blood, saliva, hair and skin cells. Moreover, when properly preserved, it can remain viable for years.
Legal sources such as the Shevin Law Group cite studies finding that DNA is 99% accurate, with errors typically attributed to human error.
Despite these developments, the Innocence Project reports that DNA evidence is available in fewer than 10% of criminal cases, largely because many crime scenes do not contain testable DNA.
Even when such evidence exists, access to testing remains inaccessible to many. Although all 50 states allow post-conviction DNA testing, the Innocence Project reports that nearly half impose procedural barriers that can prevent individuals from requesting it.
Notably, many states place a short timeframe following conviction to request DNA testing, which can affect individuals convicted before DNA testing became widely available or before more advanced techniques were developed, as noted by the Innocence Project.
In other states, testing may be restricted when an individual has entered a guilty plea. Data cited by the organization indicate that, out of more than 300 cases, 11% of clients pleaded guilty but were later exonerated by DNA evidence.
Financial costs are another obstacle cited by the Innocence Project. According to the organization, DNA testing can cost between $5,000 and $50,000 per case, depending on the number and type of tests required.
Organizations such as the Innocence Project often cover these expenses, which can limit the number of cases they are able to pursue.
Nonetheless, as the Innocence Project states, “DNA testing has become a powerful tool for linking or excluding people from crime scene evidence.”
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