Sketch of DNA

It's not fiction anymore, it's not a template yet

Evgeny Zolotov, Computerra

At the hour when you are reading these lines, the Thai police may be snapping handcuffs on suspects in a brutal murder committed near Phuket ten days earlier. The long-awaited arrest would be the best conclusion to this terrible story: it put an end to an operation that required the efforts of hundreds of law enforcement officers, caused inconvenience to thousands of tourists, and even caused an international scandal. Unfortunately, few people believe in Thai detectives: in a week and a half of the investigation, they showed themselves from the worst side and are unlikely to be able to find the true culprits. But both time and effort could be saved if there was a technology in the arsenal of criminologists that is considered fantastic, but in reality it is no longer such. DNA facial reconstruction – how do you like that?

The tragedy in question played out in the early morning of September 15 on the beach of Koh Tao island: at dawn, a passerby found two bloody bodies lying between the coastal boulders. The identities of the victims were quickly established: British tourists recognized them as their friends – David Miller, 24, and Hannah Witheridge, 23. Both were present that night at a beach party and this circumstance formed the first version: they decided to retire, got caught by robbers, resisted… Miller was stunned with a "blunt metal object" and drowned, Hannah's head was smashed with a hoe. However, the analysis of footprints in the sand and the decoding of recordings from surveillance cameras of nearby bars required adjustments. Most likely they were not a couple: Hannah was attacked a minute earlier, and Miller, heading to his hut, heard a noise and intervened.

Traces in this tragic story play a special role. There were a lot of them, but none of them makes it possible to accuse anyone with certainty. Surveillance cameras captured a running man shortly after the alleged moment of the murder, but it was not possible to make out the faces, it is only clear that he is Asian.

The only video that captures the alleged killer.

Prints in the sand showed that there were at least two attackers, but even then the police came to a dead end, even though they took all the local measurements. Finally, several cigarette butts were found near the scene of the tragedy, DNA samples on which matched DNA samples isolated from semen found on the victim. By this time it became clear that we are not talking about a simple robbery, but, alas, that's all we managed to find out in the first three days.

The police surprised everyone during this period. Its representatives were confused in their testimony (suspecting one, then two, and then six people at once), stubbornly refused to admit that Thais could have been the killers (almost literally: "Such a monstrous crime! These are probably migrants from Burma"), and the apotheosis was the accusation thrown by the Thai Prime Minister, the meaning of which was that the tourists themselves were to blame: "Did you put on a bikini? Don't be surprised to be attacked. If not ugly, of course." The prime minister then had to apologize, but this, in general, is no longer significant.

More importantly, by that time, high technology had entered the game. DNA sampling was carried out from local residents and visiting fishermen who could have been present on the island on the night of the murder (comparison with samples from the crime scene, unfortunately, did not give matches), after which Thai criminologists, having exhausted their capabilities, turned to foreign colleagues from Singapore and the USA for help.

DNA was the only serious clue. How much can this tiny piece of the human body tell about its carrier? A lot. In the simplest case, it is necessary to indicate the killer by the coincidence of "DNA fingerprints", that is, some areas in the genetic chain. Although the DNA sequences of two arbitrary Homo sapiens differ only by a fraction of a percent, comparing them (there are several ways to do this, differing in accuracy, speed and, accordingly, price) gives the probability of an erroneous match one in a billion and better. So if the killers were among the people whose DNA was taken for analysis, they would undoubtedly be calculated.

But DNA is capable of more. According to a set of genes, it is possible – albeit roughly, but quickly – to establish a person's appearance: gender, skin color, nationality, hair color. That's how they found out that the "bulls" found on the beach were smoked by two Asian men.

Unfortunately, the method of finding a killer by comparing DNA is also not without weaknesses. So the crime scene can be infected with extraneous samples: who knows who breathed on Hannah, touched her even before her death, whether the investigators worked carefully collecting evidence that morning? And for several years now, the question of the possible fabrication of a DNA fingerprint has been debated (in fact, the issue has been resolved, a genetic fingerprint can be forged by multiplying the necessary sections of the gene sequence and planting them).

It would be ideal to show local residents photos of suspects, even a sketch. Koh Tao is a small island, the community there is cohesive, everyone knows each other, everything is tied to tourism, scandals are not needed by anyone. The islanders even chipped in for a reward for information leading to the capture of the killers. But where to get a photo from? This is not a movie where shooting from a street camera can be magnified indefinitely! Here science comes to the rescue. Reconstructing a person's face from his DNA is no longer a fantasy. Scientists are working in this direction and have achieved impressive results so far.

To identify which gene is responsible for a particular physiological trait is a traditional entertainment for geneticists: researchers act like hackers, changing random pieces of genetic code and observing the consequences (or going in the opposite direction). But even on drosophila, with its primitive genome and incredible reproduction rate, this is not an easy task. After all, genes often perform several functions, are responsible for several elements of the body at once. What can we say about a person whose diversity of facial features is complex, significant and still largely misunderstood? However, since facial features are inherited, they undoubtedly have genetic "roots". And so, even theoretically, it should be possible to calculate the formation of a face based on a set of genes and, conversely, to make a set of genes based on a known face.

How this problem is solved can be judged by the report of a group of geneticists from the USA and Ireland, which was published last spring (Claes et al., Modeling 3D Facial Shape from DNA). Very simplistically, they did this. First, several dozen volunteers were measured and a three-dimensional map of the human face was built from about seven thousand points. Secondly, they borrowed information about dozens of genes, the mutation of which, as it was established reliably, affects the structure of certain areas of the skull. Thirdly, they linked all this into a computer model, which – averaging, relying on statistics – builds a face depending on the content of about twenty key genes.

Of course, there is no reason to hope for one hundred percent – photographic – accuracy: the environment in which a person lives also has an impact on facial features, skin color, and bone shape. However, the authors are confident that the forensic value of the model they built is significant. It will help archaeologists clarify how a person looked during his lifetime (in addition to the data obtained by other methods), and criminologists will draw an approximate face of the killer or victim. The resulting picture resembles a sketch: you can't recognize a specific person from it yet, but you can greatly narrow down the list of suspects compared to a verbal portrait.

Will the DNA facial reconstruction technique be used in the murder of British tourists? There is a chance – unless the Thai police decides to appoint a "scapegoat" (and it goes to that: already, allegedly, "motives" have been found in two local men who are now wanted). The case turned out to be loud enough to create a precedent. However, even if it fails this time, the era of forensic "DNA identikit" is obviously not far off. It's time to ask the traditional question: will this technology make our lives quieter?

Portal "Eternal youth" http://vechnayamolodost.ru 25.09.2014