Can we draw a portrait composed of DNA?

By reading our genes, scientists can find some of our physical characteristics. A technique used by forensic police in France.

You’re going to rob a bank tomorrow. Your plan is perfect, your equipment is infallible, and even if you lose a hair, the police could not identify you: your DNA is not stored anywhere. Really perfect? This counts without the efforts of scientists to develop the genetic composite portrait. The principle: to extract from the information contained in the DNA those that determine the morphological characteristics of the face in order to draw a composite portrait. In the United States, police have been using this technique for seven years, leading to the identification of several suspects, including Joseph Alvarez, who was convicted of a double murder in 2012. Finally, computers could directly match the faces generated in from DNA with those of a database.

A genetic predisposition to baldness and freckles

Various programs capable of establishing a composite genetic portrait have been developed by researchers, some by public laboratories, others by private companies that sell their services to the police, especially in the United States. These programs are based on the analysis of certain genetic sequences called “coders”: they are translated into proteins and produce our phenotype, that is, all our observable features, such as eye color. About fifteen genes would be the origin of the color of our irises. Do we need to analyze all these genes to see if our eyes are blue or brown? Not necessarily: instead of examining the thousands of nucleotides that make up these fifteen genes, scientists realized that they could only focus on six nucleotides, which vary from person to person. Called snips, these small genetic variations can only determine the color of the eyes with an accuracy rate of 90%, the researchers estimate. “However, there are certain shades of blue that science does not predict, or sometimes subtle differences between brown and green eyes, which do not rule out the risk of error,” says Catherine Bourgain, a geneticist at Cermes3.

The process also works for other morphological features. “We are able to deduce hair color thanks to about twenty cuts,” explains François-Xavier Laurent, head of the Biology Research and Development group at the National Institute of Scientific Police (INPS). For predisposition to freckles or baldness, compare ten to fifteen clippings. When researchers ask us to establish a “genetic robot portrait” (PRG), we do not provide them with a photo but a list of six criteria: eye color, hair, skin, predisposition to freckles and baldness. “This information does not identify anyone in the population, but it does limit the number of suspects. If the PRG claims that the suspect’s eyes are blue, the police can remove those with brown eyes.”

An authorized practice in France in a criminal investigation since 2014

Gathered within the European Face project, the researchers try to establish the list of clippings that determine the shape of the face: the distance between the eyes, the direction of the chin, the shape of the nose, and so on. “We are far from being able to offer a similar image of the face. It will probably be another ten years before the technique is perfected, ”says François-Xavier Laurent. Especially since it is now impossible to know if a person is 20 or 60 years old from their DNA. This factor has a great influence on facial features. “The older we get, the more epigenetic markers adhere to specific areas of DNA. By counting them, we could one day provide age ranges,” says the researcher. More difficult to determine than the morphology of the face: the size of the individual. There would be over 10,000 clippings involved! Not to mention the preponderant role of the environment. “We think, in a simplistic way, that height is strongly determined by our genes. If that were the case, we wouldn’t have grown so much in recent history: in two centuries, the French grew 10 cm, and the Dutch 20 cm! “The environment, especially food, plays an important role. The average height of parents explains only 50% of the variation between individuals,” says Catherine Bourgain.

The use of portraits of genetic robots in criminal investigations has been authorized in France since 2014. “This gives us the right to look at genetic sequences that can give access to information related to medical secrecy,” stresses François-Xavier Laurent. In the absence of a law regulating this practice, INPS scientists have imposed certain ethical standards. We decided to restrict our analysis to what is “visible”, such as our physical features, especially those of the face. Not all countries in Europe support this practice: if France and the United Kingdom accept it, it is still banned in Germany and Belgium.

What we can predict

These physical features are used by police in France to establish genetic compound portraits.

  • 95% eye color
  • 80% propensity to freckles
  • 100% sex
  • 95% skin color
  • 95% hair color
  • 80% propensity to baldness

Also read:

> Thanks to the analysis of our DNA, we trace the history of humanity

> Can we identify someone from a hair like in the movies?

> How is the crime scene analyzed?

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