The Combined DNA Index System, or CODIS, relies on a series of small identifying markers that themselves are not supposed to contain ancestry or other information. The genetic “fingerprint” is meant to identify the individual, without providing further data about what that persons looks like, or their race.

But some other countries allow for searching of entire DNA information which allows police to look for genes coding what a person looks like, and where their ancestors came from.

Germany, shocked at the brutal rape and murder of a young medical student apparently at the hands of an Afghan refugee late last year, is now considering a measure that would allow wider investigative use of DNA.

The furor began with the brutal October death of 19-year-old Maria Ladenburger in Freiburg. The medical student was raped and killed on Oct. 16. Her body was found in the Dreisam River the following day. The cause of death was drowning, after the sexual assault. 

The Freiburg Polizei found a strand of hair near the crime scene, which led to the killer, authorities said. The suspect was identified on Dec. 3 as Hussein K., a refugee from Afghanistan who had been allowed into Germany for asylum.

The far-right parties in the country quickly seized on the arrest as a growing danger of allowing millions of migrants into Germany. The death of Ladenburger, which had been a story for the regional press, fast became a sensational national story.

By the end of December, local legislators in the state of Baden-Württemberg proposed a bill allowing police to keep a DNA database that would allow authorities to identify suspects based on basically any kind of genetic phenotyping characteristics:

“In addition to the pedigree, sex and detection of origin the evaluation of crime scene DNA traces leading to the search of perpetrators, also in regard to further, externally (eye color, skin color, hair color, ethnicity and all other external characteristics, which, according to the current state of knowledge, to be determined),” the bill states, according to a rough Google translation.

The legislation also specifically cites the killing of Ladenburger and another young woman, 27-year-old Carolin Gruber, the following month. It’s not clear whether the two murders are related.

The bill was the focus of an editorial today by the British journal Nature, which cautioned against moving too fast in relying on the predictive-DNA methods for criminal investigations.

“These are all analyses that have been forensically validated and that police in other countries can use in their investigations. Yet if Germany wants to continue to regulate this work, and wishes to make it useful to law enforcers, it should take great care in how it words the law,” the editorial states. “Police don’t use these techniques as often as one might think, because they have to balance their cost against their predictive value. In general, they use them as a last resort, after they have worked their way through conventional investigative methods.”

In fact, there are limitations in the best genetic prediction cases. For instance, the Parabon NanoLabs Snapshot technology has made some breakthroughs in criminal cases, like a double murder in North Carolina. But its phenotyping predictive value for eye color and other features is not quite 100 percent—and cannot necessarily tell whether someone has dyed their hair, or made other changes to their appearance as it would have been dictated solely by DNA.

In the U.S., the most recent controversies in DNA database testing have focused on the use of “familial searching”—a way of finding relatives of unknown criminal suspects by searching for shared genes, and then finding comparative genetic samples through police work to effect an arrest. The time-consuming method led to some high-profile arrests—including the death penalty case against the so-called “Grim Sleeper” serial killer of Los Angeles, Lonnie Franklin, Jr., who was discovered because his son was in the criminal database.

However, recent studies have found that the U.S. database CODIS—and its limited number of markers designed to avoid race and other physical gene determinants—may actually contain some untapped ancestry information.

But some other countries do allow a full use of the DNA palette in databases for predictive value. The Nature editorial cites a 2003 law in the Netherlands which allows use of ancestry and other characteristics like skin color and eye and hair coloration to find criminals. The country had been riled by a brutal rape and murder of a woman in 1999, which was suspected to be committed by an asylum seeker from another country. The science eventually pointed to a person of northern European origin—and a local farmer was eventually convicted of the slaying.