DNA in criminology: forensic experts were taken by the throat
DNA is a setup
Alexandra Borisova, "Newspaper.Ru»The "gold standard" of criminology has been called into question: DNA examination data, as it turned out, can be fabricated, and any biology student can do it.
With the development of science and technology, investigative practice also does not stand still. From obtaining evidence by forcing a suspect to confess, law enforcement agencies have moved on to fingerprints and DNA tests. Until now, the latter were considered irrefutable proof of the criminal's guilt, especially when his blood, hair, saliva or sperm were found at the crime scene.
However, a recent work by Israeli scientists, published in the journal Forensic Science International: Genetics, completely breaks down these ideas. They showed that blood with the right DNA profile can be created artificially.
The authors of the study managed to make blood from one person's blood samples, DNA analysis of which showed that it belonged to another person. In addition, they significantly recreated the DNA profile of a certain person from the database without the participation of the donor himself. Thus, the crime scene can be completely redrawn, and the author Dan Frumkin believes that the procedure is so simple that any biology student can carry it out.
Scientists have demonstrated two methods of creating a fake DNA analysis. The first of them requires the presence of a minimal DNA sample of the "donor", that is, the person whose genetic data will eventually be found instead of the true ones. Such a sample can be obtained from a hair, from a used cup or a smoked cigarette. From a minimal amount of DNA, almost any amount of identical material can be obtained using a standard procedure – amplification of the whole genome.
After that, the scientists took the blood of another person (in fact, it can be absolutely any blood) and using centrifugation removed from it white blood cells (leukocytes) that contain DNA. After that, only red blood cells (erythrocytes) remain in the resulting material, which do not carry genetic material. DNA samples obtained by amplification are placed in this liquid, and for DNA analysis this blood already becomes the blood of the person whose hair was taken (or stolen, for example) initially.
Scientists have tested this technique in the "field" conditions. They took the woman's blood, centrifuged it and put DNA from the man's hair there. Then the resulting sample was sent for analysis to one of the leading forensic laboratories in the USA. The laboratory experts concluded that the sample contains normal male blood.
Thus, for example, the blood of a person whom criminals want to "substitute" can be easily fabricated and delivered to the crime scene and without causing any injuries to the person himself. But in this situation, it will be very, very difficult to justify a completely innocent citizen.
The second method does not require "donor" genetic material at all – it is based only on a database of DNA profiles. They are stored in the database in the form of a series of numbers and letters corresponding to the individual characteristics of 13 components of the human genome. At the first stage of the experiment, scientists cloned small fragments from a set of DNA samples of a large number of people, representing a set of possible variants of each of the components, and created a "library" of such fragments. Then they began to copy the available DNA samples, constructing them from the created fragments, as from small building blocks. They showed that, in fact, the diversity of DNA is described not by an infinite number, but only by a very large number. 245 fragments are enough to cover all combinations.
This discovery could turn the whole forensic practice upside down. In particular, it will become much more difficult to prove the guilt of rape suspects.
The first author of the work, Dan Frumkin, created the Nucleix company in Tel Aviv, which developed a commercially available test to distinguish fabricated DNA from real ones. Scientists hope that such a test will sell well to forensic laboratories.