Taking the police sketch artist's drawing into the 21st century, scientists are developing a new method that will allow cops to create an image of a suspect's face by reading the genes he leaves behind at a crime scene.
Unlocking the genes in a single strand of hair or drop of blood to construct an image of the donor's face is a process called "forensic molecular photo fitting," which could be "used to figure out what someone looks like based on their genetic markers," said Mark Shriver, an anthropologist and geneticist at Pennsylvania State University who is leading the research.
For two decades, police have used DNA to match a potential suspect to the scene of a crime, determining if the genes in a sample of blood or semen belong to an accused perpetrator.
Shriver's research takes the process one step further, not just matching a sample to a suspect but using the genetic material in that sample to create a profile of a suspect, and even a picture of his face that police can then go look for.
In addition to suspects, the same science can be used to identify victims, piecing together an image of a person's face when her remains have been severely destroyed or damaged.
"We know enough to estimate hair color, eye color, the presence of moles, skin color, hair texture, body size -- even if someone's ear wax is wet or dry," Shriver said. "We can even determine a whole host of behavioral traits like handedness -- is someone left or right handed -- all of which can help police narrow down the suspect they're looking for."
The next leap is using that information, particularly about facial features, to construct a picture of a suspect's face.
"We're working with facial images to better understand which genes determine which superficial traits," Shriver said.
Shriver said the science was still "in the research phase" and that geneticists had a better understanding of some genes' influence, such as those that determine skin color, compared to others.
"The image might be blurry in some areas, and some areas of the face where we have more information might be more defined," he said.
The Killer Was Black After All
Although creating genetic facial images is still several years away, police are already implementing investigative techniques that can create a profile of a suspect.
Shriver consults for the Florida-based DNA Print Genomics, which played an instrumental role in helping Baton Rouge police hunt down a serial killer in 2004.
Derek Todd Lee, a black man, was convicted that year for murdering seven women in two years.
Local, state and federal investigators believed for two years that the killer they were searching for was a white man.
"The general feeling was that the killer was white," said Sgt. Don Kelly of the Baton Rouge Police Department.
"I think the FBI profile indicated it was white male. The prevailing conventional wisdom was that we were looking for a white guy. Serial killers were always white, the victims were white, and killers weren't supposed to cross racial lines. At the time, we had a witness and we had a profile, both indicating we were looking for a white suspect," he said.
After getting nowhere, police turned to DNA Print Genomics.
Law enforcement officials were so skeptical that the company could determine race from DNA -- a then-unknown technique -- that they sent test samples taken from black, white and biracial police officers to the lab. When the results determined the race of each of the cops tested, the department was confident enough to send a DNA sample from a crime scene to the company.
"The DNA told us we were all wrong and should have been looking for a black suspect," Kelly of the Baton Rouge Police Department said. "That was a real turning point in the case. It turned the whole case 180 degrees and we ended up looking at Lee, a suspect early on in the case, all over again."
A Look at X and Y Chromosomes
Shriver said his method looks at hundreds of different variables across the human genome. Many of the home ancestry kits that purport to tell people from where their ancestors come have been criticized for giving participants a small slice of their genetic history, focusing only on the mitochondrial passed on by female ancestors.
Shriver, however, looks at genes along the X and Y chromosomes "to look for markers throughout the genome" that indicate different traits.