Genetic detectives

2000/09/12 Roa Zubia, Guillermo - Elhuyar Zientzia

• Genetika

DNA testing revolutionizes the field of people identification

The use of genetics was a great revolution in the field of criminology. Based on its technological viability, the DNA test was considered the definitive identification method. The genetic code itself is the biological identity document. It is a more accurate and simple test than a fingerprint test. In addition, it can be used for many other purposes. For example, it is used for paternity testing.

DNA is present in all cells of the body. It is usually removed from the blood or sperm, because in the laboratory fluids are very suitable for work. However, a crime does not always leave traces of blood or semen. Sometimes there are pieces of skin, hairs, or nails. Other times nothing. If there are any clues, detectives are usually able to extract the genetic code.

Laboratory work

In the laboratory, DNA is extracted, isolated and broken. The breakage of chromosomes from specific sites is the work of some enzymes. The obtained fractions can be distributed depending on the size. This procedure can differentiate DNA from two people, since the size of the pieces varies from person to person.

In 1982, Ronald Keith Williamson was imprisoned for raping and murdering a girl from Oklahoma. In early 1999 he was released by the results of hair and sperm analysis. Genetics denounced another suspect. Williamson is not the only one who has left prison with DNA testing. Eight people have already been sentenced to death in the United States.

However, to capture the killer your genetic code must be known previously or it may be possible to get it. That is, you cannot simply identify an unknown. However, another type of DNA can help, mitochondrial DNA. The tests mentioned so far are performed to the DNA contained in the cell nucleus.

It is the energy plant of the mitochondrial cell, where DNA is also stored. All information cannot be extracted. But all members of a family have the same mitochondrial DNA. Therefore, you can tell if the victim's family members have participated in a crime. Also, if the suspect's genetic code is not known, any of their families can model the comparison. It is also used in searches of lost children.

The advantage of this mitochondrial DNA is that it does not degrade much over time. For example, mitochondrial DNA extracted from the traces of Neanderthal men and ancient Inca mummies has been studied. Moreover, mitochondrial DNA can be extracted from more sites than usual. For example, do not search the roots of hairs, as any hair is in pieces. Despite not having all the information, the detective's research possibilities are considerably increased. A technique called minisecualization facilitates analysis. This technique has considerably accelerated the analysis of this type of DNA. Before it took three months and now, however, it is a matter of only three weeks to carry out the analysis.