There were no known eyewitnesses to the murder of a young woman and her 3-year-old daughter four years ago. No security cameras caught a figure coming or going.
Nonetheless, the police in Columbia, S.C., last month released a sketch of a possible suspect. Rather than an artist’s rendering based on witness descriptions, the face was generated by a computer relying solely on DNA found at the scene of the crime.
It may be the first time a suspect’s face has been put before the public in this way, but it will not be the last. Investigators are increasingly able to determine the physical characteristics of crime suspects from the DNA they leave behind, providing what could become a powerful new tool for law enforcement.
Already genetic sleuths can determine a suspect’s eye and hair color fairly accurately. It is also possible, or might soon be, to predict skin color, freckling, baldness, hair curliness, tooth shape and age.
Computers may eventually be able to match faces generated from DNA to those in a database of mug shots. Even if it does not immediately find the culprit, the genetic witness, so to speak, can be useful, researchers say.
“That at least narrows down the suspects,” said Susan Walsh, an assistant professor of biology at Indiana University-Purdue University Indianapolis who recently won a $1.1 million grant from the Department of Justice to develop such tools.
But forensic DNA phenotyping, as it is called, is also raising concerns. Some scientists question the accuracy of the technology, especially its ability to recreate facial images. Others say use of these techniques could exacerbate racial profiling among law enforcement agencies and infringe on privacy.
“This is another of these areas where the technology is ahead of the popular debate and discussion,” said Erin Murphy, a professor of law at New York University.
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It also opens up a new set of questions: What traits are off limits? Should the authorities be able to test whether a suspect has a medical condition or is prone to violence should such testing be possible?
Belgium and Germany do not allow forensic DNA phenotyping. The Netherlands restricts it to predicting traits that are publicly visible, like hair and eye color.
In the United States, some states prohibit testing to determine if a person has a medical condition or propensity for a disease, Ms. Murphy said. But those laws mainly pertain to samples taken from a known person, such as those in a DNA database.
Crime-scene DNA, however, is legally considered abandoned material. “There’s pretty much no law on what you can do to a crime scene sample,” Ms. Murphy said.
Related: How Accurate Are The Sketches? An Informal Test
A version of this article appears in print on February 24, 2015, on page D1 of the New York edition. Order Reprints| Today’s Paper|Subscribe
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