Everything Everywhere Daily: History, Science, Geography & More - How DNA Solves Crimes

Episode Date: September 21, 2026

For most of human history, identifying the person responsible for a crime depended on witnesses, confessions, fingerprints, and sometimes little more than suspicion. Then, in the late 20th century, scientists developed a technique that could identify an individual from microscopic traces left behind at a crime scene. It has cleared innocent suspects, identified killers decades after their crimes, and transformed modern forensic science. Learn more about DNA profiling, how it works, and how it revolutionized criminal investigations on this episode of Everything Everywhere Daily. ⁠Shop the store at ⁠⁠Shop.Everything-Everywhere.com⁠ Sponsors Hexclad Get 10% off your order at ⁠hexclad.com/DAILY⁠ Mint Mobile Save 50% on Unlimited premium wireless plans starting at $15/month at ⁠MintMobile.com/EED⁠ Quince Go to ⁠quince.com/daily⁠ for 365-day returns, plus free shipping on your order! DripDrop Go to ⁠dripdrop.com⁠ and use promo code EVERYTHING for 20% off your first order! Square Get up to $200 off Square hardware when you sign up at ⁠square.com/go/daily⁠ Babbel Go to ⁠babbel.com/daily⁠ for up to 60% off Subscribe to the podcast!  ⁠https://everything-everywhere.com/everything-everywhere-daily-podcast/⁠ -------------------------------- Executive Producer: Charles Daniel Associate Producers: Austin Oetken & Cameron Kieffer   Become a supporter on Patreon: ⁠https://www.patreon.com/everythingeverywhere⁠ Discord Server: ⁠https://discord.gg/Ds7Rx7jvPJ⁠ Instagram: ⁠https://www.instagram.com/everythingeverywhere/⁠ Facebook Group: ⁠https://www.facebook.com/groups/everythingeverywheredaily⁠ Twitter: ⁠https://twitter.com/everywheretrip⁠ Website: ⁠https://everything-everywhere.com/⁠  Disce aliquid novi cotidie Learn more about your ad choices. Visit megaphone.fm/adchoices

For most of human history, identifying the person responsible for a crime depended on witnesses, confessions, and later fingerprints. Then in the late 20th century, scientists developed a technique to identify an individual from microscopic traces left at a crime scene. It's cleared innocent suspects, identified killers decades after their crimes, and transformed modern forensic science. Learn more about DNA profiling, how it works, and how it revolutionized criminal investigations on this episode of Everything Everywhere Daily.

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I'm David Remnick, and each week on the New Yorker Radio Hour, my colleagues and I try to make sense of what's happening in this chaotic world. I hope you'll join us for the New Yorker Radio Hour wherever you listen to podcasts. Thoughtful. Exquisite. Just, you know, real. You've probably seen TV shows where forensic science units use DNA to capture a criminal. While what you see on TV might be dramatized, it is based on actual science. DNA profiling analyzes a person's DNA, the molecule that carries genetic information. It acts as an instruction manual for our cells providing the information needed to build proteins

and regulate many biological processes. We inherit DNA from our parents, and it influences many of our physical characteristics and inherited traits. In forensic science, DNA profiling involves analyzing selected regions of DNA that vary considerably among individuals. Modern forensics profiling usually examines short tandem repeats or STRs at specific locations in the genome. Investigators can then compare the resulting pattern with DNA from a suspect or with profiles

stored in a database. This can help investigators identify suspects, exclude innocent people, connect crimes committed by the same person, or established biological relationships. The development of modern DNA profiling can largely be attributed to the work of British geneticist Sir Alec Jeffreys. In 1984, while conducting research at the University of Leicester, he noticed highly valuable regions of DNA containing repeated sequences known as mini-satellites. Jefferies realized that the number and arrangement of these reports, repeated sequences varied enormously between individuals, and this variation could be used for identification.

Jeffries and his team developed radioactive probes containing short DNA sequences. These probes could bind to particular receptive regions of DNA and reveal patterns that were highly distinctive for each individual. Jeffreys called the resulting pattern a DNA fingerprint. While studying families, Jeffries also observed that children inherited portions of their DNA fingerprint from each parent. This showed that the technique could be used not only for identification, but also to establish biological relationships. The first practical use of DNA fingerprinting came in 1985 when Jeffreys used the technique to resolve an immigration dispute involving a Ghanaian

family living in Britain. One of the family's children had traveled to Ghana and was prevented from returning to Britain because immigration authorities questioned whether he was really a member of the family. Jeffreys analyzed DNA. samples from the mother, the boy, and several of her other children. The genetic patterns demonstrated that the boy was indeed her biological son. The case became the first practical application of DNA fingerprinting and demonstrated the technique's ability to establish identity and family relationships. Following the success of the immigration case, law enforcement officials began asking Jeffreys whether DNA fingerprinting might also be useful in criminal investigations.

One of the most important early cases involved the rape and murder of two teenage girls, Linda Mann and Dawn Ashworth in Leicestershire, England. Linda Mann had been murdered in 1983, while Don Ashworth was murdered in 1986. Because of the similarities between the crimes, investigators believe that the same person may have committed both murders. Police had arrested a local teenager named Richard Buckland. Buckland confessed to the murder of Don Ashworth, but denounced. killing Linda Martin. Investigators believe the crimes were connected and asked Jeffreys to

analyze biological evidence recovered from both crime scenes. At first, Jeffries was uncertain whether the technique would work with forensic samples because the original DNA fingerprinting method required relatively large quantities of reasonably intact DNA. Nevertheless, his team generated DNA fingerprints from the crime scene samples. Their results show that the same man had committed both crimes. But they also produced another surprising result. Richard Buckland's DNA did not match the DNA recovered from either crime scene. Buckland was cleared as a suspect and released from custody, becoming the first person to be exonerated from a major criminal investigation through DNA evidence. Police now knew that the murders were connected, but they still had to identify the actual killer.

Investigators launched one of the first large-scale DNA screenings in history. Thousands of local men were asked to voluntarily provide blood or saliva samples so that their DNA fingerprints could be compared with the crime scene evidence. Approximately 5,000 men were tested, but none of their profiles matched the killer. The breakthrough came when a man named Ian Kelly was overheard saying that he had provided a blood sample on behalf of another man, Colin Pitchfork. Police investigated Pitchfork and obtained a DNA sample, and his DNA matched the crime-seen evidence from both murders.

Pitchfork subsequently confessed to the crimes. In 1988, he became the first person convicted of murder, largely on the basis of DNA fingerprinting evidence. The case demonstrated both sides of the new technology. DNA evidence had prevented the wrongful prosecution of Richard Buckland, while also helping investigators identify the actual killer. Following the Pitchfork investigation, forensic DNA profiling spread rapidly during the late 80s and 1990s. One of the most important advances was the adoption of the Polymeries chain reaction or PCR. PCR allows scientists to make millions of copies of small

DNA segments so investigators can work with much smaller biological samples than Jeffrey's original technique required. Another important development, element was the adoption of short tandem repeat or STR analysis. STR profiling examines short repeating sequences at specific locations in the genome. Because modern laboratories can analyze many STR locations simultaneously, the chance of two unrelated individuals having the same profile is extraordinarily small. Modern techniques can also obtain useful DNA profiles from much smaller and sometimes more degraded samples than were possible in the early years of DNA fingerprinting.

Initially, DNA profiling was mostly used in serious criminal investigations, because the process was expensive, time-consuming, and technically demanding. But as the technology became faster and cheaper, governments began creating DNA databases that allowed investigators to compare crime-scene DNA with profiles collected from known individuals. One of the most important developments in the United States came with the DNA Identification Act of 1994. The law authorized the FBI to establish a National DNA Index. The FBI operates the combined DNA index system known as CODIS, which allows participating federal, state, and local

laboratories to store and compare DNA profiles. The national level of CODIS is known as the National DNA Index System, or NDIS, which became operational in 1998. COTUS allows DNA evidence from one crime scene to be compared with evidence from other crime scenes as well as profiles from known individuals. A match can help investigators identify a suspect or connect crimes across jurisdictions. The system contains several different categories of DNA profiles. These include profiles from convicted offenders, certain arrestees and detainees, forensics evidence recovered from crime scenes, missing persons, unidentified human remains, and relatives of missing persons. By the mid-2020s, the National DNA Index System contained tens of millions of profiles, making it one of the

largest forensic DNA databases in the world. DNA databases can also connect crimes committed by the same person in different locations or at different times. Research suggests that DNA databases may also have some deterrent effect. Studies have found modest evidence that inclusion in a DNA database may reduce recidivism for certain crimes, although their clearest benefit is increasing the likelihood that repeat offenders will be identified. DNA evidence can also be used to identify biological relatives of an unknown suspect. One technique is known as familial searching. Instead of looking for an exact DNA match in a law enforcement database,

investigators search for profiles that share just enough genetic information to suggest that the person may be a close biological relative of the unknown suspect. Another technique known as investigative genetic genealogy uses genetic genealogy databases in traditional genealogical research to identify an unknown person's relative and construct family trees. These techniques have allowed investigators to solve crimes that remained unsolved for decades. One of the most dramatic modern examples of DNA profiling solving a cold case involved the Golden State Killer.

In the 1970s and 80s, a 70s, a cell. serial killer committed a long series of rapes, murders, burglaries, and other crimes across California. Investigators recovered biological evidence from several crime scenes, but for decades, the DNA didn't match anyone in traditional law enforcement databases. The breakthrough came through investigative genetic genealogy. The investigators uploaded genetic information from the crime scene DNA to GED match, a genealogy database that at the time allowed users to compare their DNA with other participants. The search identified distant relatives of the unknown killer.

Genealogists and investigators then used public records to construct family trees, connecting those relatives to common ancestors. Investigators gradually narrowed the list of possible suspects based on characteristics such as age, sex, geographic location, and family relationships. The investigation eventually focused on Joseph James DeAngelo, a former police officer who had lived in several of the areas where the crimes were committed. Police placed DeAngelo under surveillance and secretly collected items that he had discarded. DNA obtained from those items matched genetic evidence recovered from the original crime scenes.

DeAngelo was arrested in 2018. He later pleaded guilty to 13 murders as part of a plea agreement and admitted responsibility for numerous other crimes. Investigators have connected the Golden State Killer crime spree to more than 50. sexual assaults. DNA profiling itself can be extremely reliable when it's performed correctly, but mistakes can occur during the collection, handling, processing, or interpretation of evidence. And one of the best examples of this was the so-called Phantom of Heilbron. Beginning in the 1990s, DNA from an unidentified woman appeared at dozens of crime scenes across

Germany, Austria, and France. Investigators believe that the same woman might be able to be. The same woman might somehow be connected to a large number of crimes, including murders. After years of investigation, authorities discovered that the mysterious DNA did not belong to any criminal at all. It belonged to a woman who worked at the factory that manufactured the cotton swabs used by police investigators. The swabs had been contaminated during production. The case demonstrated that even highly accurate DNA technology can produce misleading results, if evidence becomes contaminated. Problems can also occur when DNA samples contain genetic material from multiple individuals.

These mixed samples can be difficult to interpret, and analysts sometimes have to make statistical judgments about whether a person's particular DNA is consistent with the mixture. Privacy is also another major concern. DNA contains far more information than a fingerprint. Genetic material can potentially reveal biological relationships, and, depending on the type of of testing performed, information about ancestry and some inherited characteristics. Large government DNA databases raise questions about how to collect, store, search, and retain genetic information. Familiar searching can also raise privacy concerns, as people who have never submitted DNA to law enforcement may come under suspicion because a relative is already

in the database. DNA profiling has fundamentally transformed forensic science. It can identify perpetrators, eliminate innocent suspects, connect crimes separated by years or thousands of miles, and reopen cases that once appeared impossible to solve. DNA profiling has become one of the most powerful investigative tools ever developed, and as genetic technology advances, both its capabilities and the debate surrounding its use, will continue to grow. The executive producer of Everything Everywhere Daily is Charles Daniel, the Associate producers are Austin Otkin and Cameron Kiefer. Research and writing for this episode was provided by Olivia Ash. My big thanks go to everyone who supports the show over on Patreon. Your support helps

make this podcast possible. And I also want to remind everyone about the community groups on Facebook and Discord. This is where everything happens that's outside of the show. As always, if you leave a review on any major podcast app or in the above community groups, you two can have it read on the show.