Painting a Mug Shot with Genetics: A Spotlight on DNA Phenotyping

By Stefanie Veneziano

In 1965, nine out of ten murders were solved in the U.S. Since then, the rate of solved homicides has gone down significantly, according to the Pew Research Center. Today, only two out of three murders are resolved.

Despite what crime shows make it seem like, clearing killings has become harder in recent decades according to homicide detectives. Some attribute it to higher standards for charging someone and others blame a lack of public trust in the system, according to an NPR report.

One thing is sure: scientific advances have helped solve many murders that 50 years ago would have gone unsolved. In criminal forensics, the use of DNA evidence is relatively new. The first case to prove a death using DNA profiling was in 1987. Since then, thousands of cases have been solved using biometrics such as matching fingerprints, hair, sperm, or iris scans.

Until recently, DNA evidence has only been able to confirm identities from matching samples. In other words, the genetic material found at crime scenes has only been valuable if there were already a suspect in the case. Without any leads, a perpetrator’s DNA would be useless unless his or her identity was already confirmed.

Today, forensic technology allows investigators to use genetic material to build the identity of a person and determine leads by using the DNA phenotyping.

What Is DNA Phenotyping?

DNA phenotyping is used to predict an organism’s physical characteristics by using information collected from its genetic code. The sequence of genomes in any person’s DNA can indicate possible observable traits, such as hair color, eye color, face shape, skin color, sex, and more.

The primary and most reliable traits determined from phenotyping are facial shapes. Researchers from Pittsburgh University, Stanford University, and Pennsylvania State University, as well as Katholieke Universiteit Leuven in Belgium, published their findings in February 2018 which showed that 15 genes determine unique facial features, including the prominence of cheekbones, the distance between eyes, and chin shape. Seven of these genes are linked to the shape and length of the nose, which has been difficult for forensic scientists to reconstruct using only cranial DNA information.

Because specific genotypes are more common among certain ethnicities, DNA phenotyping can also determine an individual’s geographic ancestry, although some skeptics claim that this use of DNA phenotyping in forensics can lead to racial profiling. Other than using genetic material to predict the physical appearance of criminals or victims in forensic investigations, there are several other applications for DNA phenotyping technology.

Already, biotechnology companies like 23andMe sell DNA test kits to individuals who want to learn about their biogeographic ancestry independently. This popular service allows people to send in saliva swabs and find out how much of their genetic makeup is from different parts of the world. This type of technology is also used to determine paternity.

DNA phenotyping has other applications in personalized medicine. By knowing an individual’s genetic makeup, doctors can predict how a patient’s body will respond to certain drugs and prescribe accordingly. In what is known as pharmacogenomics, doctors and pharmacists can observe a patient’s genotypes to predict the most efficient use of drug treatment while minimizing adverse effects and avoiding trial-and-error prescriptions.

For now, DNA phenotyping is primarily associated with forensic investigations. This technology has already helped find the identities of victims and criminals in several homicide cases. Companies like Parabon NanoLabs offer DNA phenotyping services to law enforcement officials to help solve identities in criminal cases.

DNA Phenotyping for Identifying a Victim

In June 2017, skeletal remains were found under a tarp in Glen Burnie, Maryland. The body was so decomposed that investigators could not identify the victim, except for the medical examiner’s findings that the victim was a female in her 20s. Months later, the county police used DNA phenotyping from Parabon NanoLabs to determine that the victim was of African descent, had dark brown skin, brown eyes, black hair, and freckles.

The Baltimore City Police Department saw the reconstructed image of the victim based off of the DNA information, who bore a striking resemblance to Shaquana Caldwell, a 26-year-old Baltimore resident who had been missing for about a month. The medical examiners compared the dental records of Caldwell to skeletal remains found in Glen Burnie and found a match.

Shortly after, Caldwell’s boyfriend, Taras Caldwell was arrested. He confessed to strangling her during an argument and disposing of her body in the woods.

DNA Phenotyping for Identifying a Criminal

In November 2009, the body of 19-year-old Sierra Bouzigard was found lying near a country road in Lake Charles, Louisiana. Investigators pulled evidence from the crime scene and began reconstructing her final hours. One piece of evidence, in particular, would help solve the case: skin tissue underneath the victim’s fingernails as a result of her struggling for her life. The DNA sample was then sent to the lab for analysis.

At the same time, investigators were hunting down a different lead: a phone number she dialed before she was killed. The number led the police to a group of undocumented Mexican workers, so they got warrants for DNA swabs. However, none of them matched the sample from the crime scene, and investigators found no match in the FBI database of prior felons, so the case went cold.

In June 2015, the investigation was reopened thanks to DNA phenotyping. While investigators still believed the killer to be of Hispanic origin due to their previous lead, the DNA-generated snapshot from Parabon Labs showed a man of northern European descent with pale skin, freckles, brown hair, and light eyes. This revelation completely changed the investigation’s path.

“We kind of had to take a step back and say all this time, we’re not even in the right direction,” Sheriff Tony Mancuso told National Geographic. Two years later, the police charged Blake A. Russell with the crime following a tip based on the portrait. Russell’s DNA sample matched that of the one at the crime scene.

The Case Against DNA Phenotyping

Even though DNA phenotyping has helped solve several mysteries, critics remain skeptical about this technology to solve criminal cases. Creating an image from phenotyping costs thousands of dollars, and the physical traits produced are nothing more than predictions that do not guarantee an individual’s appearance. Many defining characteristics of someone’s appearance such as facial hair, dyed hair, scars, tattoos, weight, and height, are not found in one’s DNA.

Because phenotyping can only predict a snapshot image of an individual with certain physical characteristics, many believe that its use can lead to racial profiling. The New York Times published a report interviewing DNA experts about the technology, and many raised concerns about its selective application:

“This leads to a technology that is better able to make faces that are African-American,” Dr. Duana Fullwiley, an associate professor of anthropology at Stanford University, told the newspaper. Others also noted that Parabon had not, at the time, published any research in peer-reviewed journals validating its method. What’s more, DNA phenotyping is not allowed in courts because the technology is still nascent.

While the use of DNA evidence in criminal investigations has a large margin of error today, the advancement of this technology can lead to a potentially higher rate of accuracy in the future. Proponents of forensic DNA phenotyping argue that its applications can be invaluable in bringing justice to unsolved cases, especially for victims and their families. Not only is the technology useful in forensics, but it can help save lives through customized medicine and more.