DNA: Solving Crimes of the Past, and of the Future

The advent of modern DNA testing, sequencing, and analyzing techniques have also invigorated another area of science: forensic testing. Even 30 years ago, the science of genetics, genealogy, and DNA sequencing were poorly developed. However, in the decades since, forensic science has taken full advantage of the advancements within genetics.

With these advances in DNA testing technologies, many cold cases have since been solved using simple, accurate, advanced techniques. Modern DNA testing uses ultra-fast sequencing technology. When it used to take weeks to months to sequence a sample of DNA, it now takes only hours.

But why are DNA sequencing technologies so crucial to forensic science?

DNA is Unique to Every Person

Unless you have an identical twin, the sequence of nucleotides within your DNA is unique to YOU! That means that if you leave DNA evidence at a crime (think blood, hair, or skin cells) you can easily be identified as the perpetrator of the crime.

For many decades, science has recognized that DNA is unique to every individual. For example, the FBI has consistently used the CODIS database to identify and prosecute criminals based on their DNA profile. However, this database is small. It is mainly limited to felons and people who have already been convicted of a crime. Unfortunately, this system had no way to identify people who had never been convicted of a crime. Worst still, many serial killers, serial rapists, and other regular criminals had never been caught. That means that even if these criminals left DNA at a crime scene, there was no way to identify them.

How can a DNA test help solve a crime?

Enter the age of modern genomics. With rapid and thorough DNA tests conducted by a number of companies, the amount of genetic data available expands exponentially. Further, analysis by genealogists led to a number of breakthroughs involving family trees.

You see, each person gets their DNA from only two sources: their parents. Because of this simple fact, a person’s DNA profile can be assumed using their two parents, or even two distant relatives. Further, with the mass collection of DNA for at-home DNA testing, the databases of non-criminals grow every day. And, well, everyone is related to someone.

Using this knowledge, forensic scientists took a bold step. They started analyzing family trees to see which families were most related to the samples they had gathered at crime scenes. Further, modern DNA testing techniques allowed scientists to test the entire genome. This includes autosomal, mitochondrial, Y-DNA, and X-DNA testing. With all of these sources, DNA databases, and modern computers, solving a cold case with DNA became a simple matter of matching. Find the family the sample belongs to, and more often than not you can find the criminal. Don’t believe it? Take a look at several cold cases that have been solved in the last decade.

Cases That Have Been Solved Using Modern Genealogy

The Golden State Killer

Dubbed “the Golden State Killer” by a journalist, this serial rapist and murderer had been loose in California for decades before DNA evidence finally caught up with him. Joseph James DeAngelo had been a police officer and had served in Vietnam. Before DNA profiling and genotyping, he was never on the radar as a potential suspect for over 13 murders and 50 rapes in California.

However, that all changed after forensic scientists started using all the modern DNA tools available to them. In 2018, forensic scientists used DNA evidence they had collected at a crime scene, and submitted the DNA to GEDmatch, an online tool for comparing DNA and finding relatives.

The scientists were able to use the platform to find the killer’s family members, who had willingly submitted their DNA profiles to the platform. Because DNA comes from parents and is shared by relatives, the scientists quickly identified the killer’s family. After gathering information on the family, and their whereabouts during the killings, they were able to easily identify DeAngelo as the prime suspect. Though he had been a police officer, he had served in the exact areas where the murders had taken place. Police quickly found DeAngelo and took a sample of his DNA. It was an exact match to the DNA left by the killer at various crime scenes.

The Murder of Linda O’Keefe

While the serial killer in the previous section had left DNA evidence across multiple crime scenes, not all criminals were so bold. In 1973, a young girl named Linda O’Keefe was killed as she walked home from school in Southern California. A turquoise van stopped beside Linda, and that was the last time anyone saw her alive.

No one was ever arrested, and no new leads were found. That is, until scientists understanding genetic genealogy got involved. Using DNA evidence collected at the scene, prosecutors were able to match the DNA from the scene to a number of people in a genetic database. These clues led them to identify James Alan Neal as the killer, nearly 46 years after he had committed the crime. Using his DNA from the crime scene, Neal’s family was identified; even after he had moved to Florida and legally changed his name. You know what they say: there is no rest for the wicked.

Looking Ahead

While many more cold cases have been solved this way, not all crimes contain DNA evidence. These crimes, unfortunately, will continue to go unpunished until we find new forensic science techniques. However, criminals beware! If you leave as much as a hair at the scene of a crime, police now have a proven, tested method for catching you.

Given the fact that millions and millions of people have taken a genetic test, and the fact that most of these tests end up in large genetic databases, almost anyone can be identified by genetic genealogy. Even if you, or an immediate family member, has never submitted a DNA sample, it is likely that one of your distant cousins have. Given this advantage, forensic scientists can track the DNA of almost every person in the world.

For the moment, at least, it seems that criminals have finally met their ultimate match: genetic genealogy. Using only a few segments of DNA collected at a crime scene, prosecutors and law enforcement agencies will be able to find anyone, anywhere who has committed a crime.

Notify of
Inline Feedbacks
View all comments