Image copyright Other Image caption The face was based solely on the genetic make-up of presenter Gabriel Weston

The face of a killer constructed from DNA left at the scene of a crime: it sounds like science fiction. But revealing the face of a criminal based on their genes may be closer than we think.

Today scientists are using genetic markers from DNA to build up a picture of an offender's face, a process known as molecular photo fitting.

A DNA profile is only useful to detectives if a match can be found on a database.

As surgeon Gabriel Weston explains in the BBC series Catching History's Criminals: The Forensics Story, this technology offers the tantalising prospect of generating a face from nothing more than a few cells.

To find out just how effective this process can be, DNA was extracted from Gabriel's saliva and the results sent anonymously to a group of scientists in Belgium.

From that data they set about building a picture of Gabriel's face - as predicted by her genes. The question was: Would it look anything like her?

The job of turning the cells in her saliva into a picture of her face was carried out by Dr Peter Claes, a medical imaging specialist at the University of Leuven.

Along with colleagues in the US, he's built up a database of faces and DNA. And armed with this information, he's able to model how a face is constructed based on just 20 genes.

It is possible to judge just how much the picture of Gabriel's face - based on her genetic makeup - looks like her by comparing it to her actual image.

Image copyright Other Image caption Gabriel's DNA results were sent anonymously to a team of scientists in Belgium

Dr Claes believes it contains a lot of information that would be useful to detectives: "I can tell you that your eyebrows are sticking forward more, and your chin as well," he explains.

"You have a very prominent specific chin compared to an average European, which in my eyes is not a bad result. You do tend to have flat cheeks, but of course that's a tricky area to actually predict accurately because it's heavily based on diet, which is an environmental factor."

If this predicted face is superimposed over a photo of Gabriel, the accuracy of the technique is revealed.

The eyes, nose, mouth and chin are all in roughly the right place. But the features are more rounded than in reality.

Image caption Scientists were able to compare the faces when they were superimposed

At the moment, police couldn't publish a molecular photo-fit like this and hope to catch a killer. But that's not how Dr Claes sees the technique being used in a criminal investigation.

"If I were to bring this result to an investigator, I wouldn't necessarily give him the image to broadcast. I would talk to him and say okay, you're looking for a woman, with a very specific chin and eyebrow structure.

"So if you're having suspects or candidates that you're looking for, just focus on those."

This may be new science, but Dr Claes and his colleagues are rapidly developing the technology.

The number of genes used is being expanded from 20 to 200, and is seems clear that molecular photo-fitting is only going to become more accurate in the coming years.

Catching History's Criminals: The Forensics Story is presented by Gabriel Weston and can be seen on BBC4 at 2100 on Thursday 18 June