Police first used DNA in criminal cases in 1986, when detectives in Leicestershire, England, asked geneticist Alec Jeffreys to analyze evidence from two rape-murders. That investigation produced two firsts within about two years: Richard Buckland became the first person cleared by DNA evidence in 1986, and Colin Pitchfork became the first person convicted through DNA profiling in 1988. The technology crossed the Atlantic almost immediately. On November 6, 1987, an Orlando jury convicted Tommie Lee Andrews of rape, making him the first person in the United States found guilty on the strength of a DNA match.
The Leicestershire Investigation That Started It All
Two teenage girls had been raped and murdered in the same part of Leicestershire three years apart: Lynda Mann in 1983 and Dawn Ashworth in 1986. A local teenager named Richard Buckland confessed to the Ashworth killing under interrogation. Investigators suspected the two crimes were connected and turned to Jeffreys, whose laboratory at the University of Leicester had developed a method of comparing DNA samples. When Jeffreys tested crime scene material against Buckland’s blood, the profiles did not match. Buckland was released, the first person ever exonerated by DNA evidence.1National Library of Medicine. Alec Jeffreys and the Pitchfork Murder Case: The Origins of DNA Profiling
Police then tried something no force had tried before. They asked roughly 5,000 local men to give blood samples for comparison with the crime scene DNA. Colin Pitchfork, a baker from the area, persuaded a coworker to give a sample in his place. The ruse fell apart when the coworker was overheard talking about it in a pub. Pitchfork’s own sample matched both murders. He was convicted and sentenced to life in prison in 1988, the first conviction in the world secured through DNA fingerprinting.1National Library of Medicine. Alec Jeffreys and the Pitchfork Murder Case: The Origins of DNA Profiling
The First U.S. Conviction: Florida, 1987
American law enforcement did not wait for the Pitchfork trial to adopt the technique. On November 6, 1987, Tommie Lee Andrews was convicted of rape in Orlando, Florida, becoming the first person in the United States found guilty using DNA profiling. Investigators compared DNA from Andrews’s blood to semen recovered from the crime scene, and a molecular geneticist testified at trial that the two profiles matched. Andrews received a 22-year sentence for rape, aggravated battery, and armed burglary. The verdict signaled to American prosecutors that DNA evidence could survive a jury trial and carry a conviction.
The Science That Made 1986 Possible
DNA could not have entered a criminal investigation before 1986 because the method did not exist. In 1984, Jeffreys and colleagues at the University of Leicester were studying inherited variation in DNA when they noticed something striking. Certain repeating sequences differed so dramatically from one person to the next that the pattern functioned like a biological fingerprint. Apart from identical twins, no two people shared the same profile.2University of Leicester. DNA Fingerprinting
The specific technique Jeffreys developed relied on restriction fragment length polymorphisms, or RFLPs. Enzymes cut DNA at specific points, and the lengths of the resulting fragments varied from person to person. Comparing fragment patterns could tell whether two samples came from the same individual. The method was slow and required a substantial amount of intact DNA, which limited its usefulness on degraded crime scene material, but it worked.1National Library of Medicine. Alec Jeffreys and the Pitchfork Murder Case: The Origins of DNA Profiling It was the first time a laboratory could tie a specific person to a biological sample with near certainty, and it reached the Leicestershire police within two years of the discovery.
Getting DNA Evidence Through the Courts
A new forensic technique has to clear a legal hurdle before a jury ever hears about it. In the late 1980s, American courts evaluated novel scientific evidence under Frye v. United States, a 1923 federal appeals court decision that admitted scientific testimony only if the underlying method had gained “general acceptance” among experts in the relevant field. A handful of states still apply Frye. In 1993, the Supreme Court replaced that test in federal courts with Daubert v. Merrell Dow Pharmaceuticals, which made the trial judge a gatekeeper responsible for evaluating whether a method has been tested, peer-reviewed, has a known error rate, and is generally accepted.3Justia Law. Daubert v Merrell Dow Pharmaceuticals Inc, 509 US 579 (1993) Most states have since adopted Daubert or a close variant.
DNA profiling cleared both standards relatively quickly. The underlying biology was well-established, error rates could be quantified, and the published literature was substantial. By the mid-1990s, challenges to the admissibility of DNA evidence itself had largely faded. Disputes that remained tended to focus on laboratory handling, contamination, or statistical interpretation rather than on whether the science belonged in a courtroom at all.
A separate constitutional question concerned collection rather than analysis. In 2013, the Supreme Court held 5–4 in Maryland v. King that taking a cheek swab from someone arrested for a serious offense is a reasonable booking procedure under the Fourth Amendment, comparable to fingerprinting or photographing.4Justia Law. Maryland v King, 569 US 435 (2013) That ruling validated the state laws authorizing DNA collection from arrestees, not just from people already convicted.
From a Single Case to a National System
DNA evidence stopped being extraordinary and became routine once databases allowed profiles to be compared across jurisdictions. Congress passed the DNA Identification Act in 1994, authorizing the FBI to build a national index of DNA profiles.5Federal Bureau of Investigation. Federal DNA Identification Act In October 1998, the FBI launched the National DNA Index System, which runs on software called the Combined DNA Index System, or CODIS.6Federal Bureau of Investigation. CODIS and NDIS Fact Sheet
CODIS works on three tiers. A local crime lab enters a DNA profile from a crime scene, compares it against its own records, uploads it to the state database, and ultimately contributes to a weekly upload to the national index, where profiles are searched against offender records from all 50 states. When the software reports a match, laboratories verify the result before investigators act on it.7Federal Bureau of Investigation. The FBI and DNA, Part 1
As of late 2025, the national index held more than 19.2 million offender profiles, over 6.1 million arrestee profiles, and roughly 1.4 million forensic profiles from crime scenes. The system had produced more than 781,000 hits and aided over 758,000 investigations.8Federal Bureau of Investigation. CODIS-NDIS Statistics The gap between the Leicestershire investigation and a routine database hit is less than a generation.
The Other Side of the First Case
It is worth remembering that the first criminal use of DNA cleared a suspect before it convicted one. Buckland had confessed. Without Jeffreys’s analysis he would almost certainly have gone to prison. That dual function has defined the technology ever since. The Innocence Project, which has led post-conviction DNA testing efforts in the United States since 1992, reports that 205 of its clients have been exonerated by DNA evidence as of early 2026, many after serving decades. Post-conviction DNA testing of preserved biological evidence is now a recognized legal process in every state, and in a significant number of exonerations the same test that cleared the wrongly convicted person identified the actual perpetrator through a CODIS match.