How Genetics is Used in Criminal Investigation

Movies and fiction have been made about DNA and how it can be manipulated to create stratified societies. They have presented a world far darker (and scarier) than it is. Beyond science fiction, though, genetics and the DNA behind it have the potential to make work in health and law easier for practitioners.

DNA, or deoxyribonucleic acid, is comprised of proteins that are the building blocks for the genetic code. In humans, the code is defined by four nucleotides (adenine, thymine, cytosine, and guanine), nucleotides that create a ladder giving instructions on the human genetic code. Every rung on the ladder explains how we get our traits, including our hair, eye, and skin color, in addition to other phenotypic traits.

More modern methods of DNA analysis involve what is known as a polymerase chain reaction, commonly called PCR. While DNA analysis has been around for far longer than now, advances in DNA analysis, such as PCR, allow labs to amplify billions of DNA strands which can be analyzed closer later. This DNA analysis method is said to be quicker than traditional methods and more accurate in analyzing DNA from different vantage points.

Most people are familiar with the use of DNA to determine paternity, as seen on many daytime family court shows where the paternity of a child is in question. Furthermore, programs such as PBS’s Finding Your Roots use DNA technology to help celebrities find their family lineage. As this technology has advanced, everyday people have discovered their family lineage, some heritages dating back more than a century and to different parts of the world.

However, tracing our family lineage is not the only use for genetics and DNA.  DNA and our genetic code have also been used in criminal investigations for some time. As early as the 1980s, states enacted legislation requiring that law enforcement agencies collect samples from people convicted of sexual and violent crimes. The Federal Bureau of Investigation established guidelines for sample collection and forensic analysis.

These agencies have turned to DNA because traces of DNA found at crime scene investigations are more accurate at placing an individual in certain locations. After all, DNA is unique to each individual, except in the case of identical twins who share the same DNA. The way law enforcement uses DNA is to collect samples of hair, blood, bone, teeth, saliva, and other samples to compare them against other DNA profiles. After analyzing the samples, they entered them into a database. Investigators typically collect these samples to eliminate or identify individuals who might have been at the scene of a crime. However, as a part of criminal investigation, genetics has evolved to have other uses.

Uses of genetics (DNA) in criminal investigation

DNA technology has proved to be a valuable resource in law enforcement. Not only has it helped agencies with decades-old closed cases, but it has also helped agencies more accurately place suspected criminals at the scene of the crime. Read below to see some other ways that genetics has served in helping law enforcement keep track of crime.

Information sharing 

DNA technology has allowed state and federal agencies to track crime accurately in the country. The Combined DNA Index System (CODIS), used by federal, state, and local agencies, houses the DNA profiles of anyone ever suspected of a serious or violent crime. This information is useful because it allows law enforcement agencies at all levels to share information.

DNA fingerprinting

The way crimes are solved using genetics is through a process called DNA fingerprinting. Long before DNA, PCR, and using genetics, detectives solved crimes through fingerprints. Everyone’s fingerprints are unique, and so one of the ways detectives placed a person at the scene of a crime was to see if the suspect left fingerprints on any of the surfaces.

In the same way, DNA is a genetic fingerprint that contains the human genome (short tandem repeats or STRs) plus regions on the DNA strand that are unique (repeats that vary) to everyone. In a nutshell, using PCR, law enforcement labs will collect 20 STRs to create a DNA fingerprint. If a person is suspected of a crime, law enforcement collects a sample from the suspect and compares it with DNA extracted from samples found at the crime scene.

If the profiles of all 20 STRs do not match, the likelihood is that the DNA sample of the suspect and that taken at the crime scene are not from the same person and the person would be excluded as a source of DNA from the crime scene. However, if there is a match across all STRs, the technicians must make a statistical calculation to determine the frequency of the STR in the general population. Usually, this also means that the sample at the crime scene matched the sample taken from the subject because the chance that two people have the same STR is one in a quintillion or one in 1,000,000,000,000,000,000.

Investigative genetics genealogy

Another way that genetics have helped law enforcement is through using genetic genealogy that looks at relatives to narrow down a suspect. The methodology used to solve cases involves taking the sample collected at the crime scene and comparing them to samples that might appear on other genealogy sites, for example, 23 and Me, Ancestry, and GEDmatch. This process is probably helpful in finding suspects when a sample has been collected but cannot be identified.

So, law enforcement has not identified a suspect, but they have a DNA sample they can analyze. Working backward, the agency will take the DNA information provided from the sample and upload it to databases, both official and commercial ones like the abovementioned. Once the sample has been uploaded, a comparison can be made to others in the four databases. 

Ideally, if there is a match, the investigator can connect the person to others in the database. For example, the suspect’s DNA matches a second cousin and a half-sister, giving investigators direction on where to start looking. At this point, the investigators only need to narrow down the area focus to find relatives whose DNA is a close match with that of the suspect’s DNA. 

In the case of the Golden State Killer, for instance, law enforcement applied this same methodology in tracking down a former police officer accused of the killings. The investigators simply constructed the suspect’s family tree after uploading his DNA. 

The methodology has been so successful that law enforcement has closed several cases involving violent acts. While the process can be lengthy, labor intensive, and costly, data reveals that cases from the 1970s and 1980s have been closed using the method. Seeking out family members to find a suspect’s identity makes it possible to gather evidence from a suspect and place them at the scene of the crime compared with not having a suspect at all, regardless of the cost, time, or labor. 

Identifying victims

For investigators, solving violent crimes begins when a body is found. Often, law enforcement is not given any clues as to who the victim is because the person is left without identification. These individuals are assigned the monikers John or Jane Doe, depending on the gender of the person.

Genetics and DNA make it possible for law enforcement to identify these nameless people. Further, initiatives such as the Jane Doe Project, a nonprofit venture, help identify victims of cold cases. Since its inception, the Jane Doe Project has identified over 40 victims using forensic genealogy. 

Criminology educational programs and genetics

Criminology seeks to study criminal behavior by looking at motivations, among other factors. Before the last decade or so, criminology avoided using genetics as a topic in explaining criminal behavior because certain racial groups wanted to avoid it becoming a topic of eugenics, which led to concerns regarding racism. These concerns were backed up by previous instances when race was used to explain criminal behavior.

However, today’s genetics and DNA seem to offer academics more than reducing criminal behavior to race. In fact, because the technology has the potential to help researchers to determine, to the exact DNA molecule, what genes influence behaviors typically associated with crime, researchers stand a chance of figuring out ways to use genetics to deter, maybe prevent, crime, especially violent crime.

When the entire genome was sequenced nearly two decades ago, criminologists believed that this technology might provide answers to social problems, for example, alcoholism. More significantly, they are also considering using this fascinating way to look at DNA to make predictions regarding criminal behavior and whether it means criminality can be inherited. Genetics have helped theorists weave modern theories related to crime together.

Today, researchers and academics have realized that genetics can play a role in criminal behavior. More than 100 studies support the fact that, to a point, genetics (and environment) play a role in whether an individual has the propensity to commit a crime. Universities such as Wilfrid Laurier offer criminology programs Canada online that explore this new science that not only can be used to place suspects at the scene of the crime but also is predictive in nature.

One longitudinal study followed toddlers in 1972 and looked at children who displayed instances of less self-control. They then made predictions about the 1,000 children who were studied that said that those who exhibited less control were more than likely to have committed some crime over 30 years later. Researchers found that 43 percent of children who showed less self-control (were in the lowest fifth) were convicted of some crime. This was compared with the 13 percent who scored in the highest fifth who were not convicted.

This study illustrates that genetics can play a role in how individuals respond. Conversely, many researchers acknowledge that the environment plays a role in determining whether a person will turn to criminal acts. Ultimately, though, the use of genetics and DNA as a part of studying criminology is likely to continue to grow as technology advances and as researchers learn more about how DNA instructs not only our physical appearance but also our behaviors.

Final words 

Genetics and DNA have ushered in a new era of law enforcement. In the past, law enforcement, victims of violent crimes, and their families were at the mercy of the crime scene to tell them the narrative of what happened to the victim. As is the case with many cold cases around the country, everyone had to wait for information to come in related to what happened and who might have been at the scene of the crime.

With DNA sequencing and forensic genealogy, law enforcement can now more accurately find suspects and place them at the scenes of unsolved crimes. This tool has made it possible for law enforcement agencies to share information, making solving crime more efficient for detectives. More importantly, it has reduced the errors in identifying suspects, and in some cases, it has been used to exonerate innocent people. DNA sequencing, PCR, and investigative genetic genealogy have made it possible to find suspects who, in former times, escaped simply because there was no way to connect them to others in the community. Finally, it has also made it possible to give names to nameless people.

Outside of law enforcement, however, genetics plays a role in criminology. In academia, genetics has played a role in helping researchers make predictions about future behaviors, in addition to understanding the importance and impact of the environment on our genes. Many researchers find that studying genetics and the human genome in the context of making these predictions can lead to answering questions regarding whether genetic predispositions should have a role in sentencing people convicted of crimes. Other ways that genetics can play a role in criminology relates to figuring out how genetics can be used to create rehabilitation programs that cater to the needs of inmates or former criminals. The study also opens the possibility of identifying children and adults with certain genetic markers.  

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