DNA

Over the past decade, deoxyribonucleic acid (DNA) has emerged as one of the most powerful tools in the criminal justice system. When biological evidence is available, DNA can identify perpetrators with exceptional precision. At the same time, it plays a critical role in excluding innocent suspects and overturning wrongful convictions. As a result, DNA technology has become central to promoting accuracy and fairness in criminal investigations and prosecutions.

Numerous cases illustrate its impact. In 1999, investigators in New York used DNA evidence to connect a single individual to at least 22 sexual assaults and robberies that had plagued the city. In 2002, authorities in Philadelphia, Pennsylvania, and Fort Collins, Colorado, relied on DNA analysis to link and solve multiple crimes—including rapes and a murder—committed by the same offender. Similarly, in the 2001 Green River killings, DNA evidence provided a decisive breakthrough in a long-unsolved series of murders, despite years of intensive investigation and significant financial resources.

DNA is typically applied in two primary ways. When a suspect has been identified, that individual’s DNA sample can be compared with biological material collected from the crime scene to determine whether there is a match. When no suspect is known, crime scene evidence can be analyzed and searched against profiles stored in DNA databases to help identify the perpetrator. Additionally, DNA databases enable investigators to link evidence across multiple crime scenes, revealing patterns and connections between cases.

Forensic DNA analysis continues to advance rapidly. Ongoing research and development aim to equip crime laboratories with tools that allow faster and more efficient testing. More compact, rapid, and cost-effective technologies will reduce infrastructure costs while expanding laboratories’ capacity to process a greater number of cases in a timely manner.