Fidelity to the fingerprints

2000/09/05 Roa Zubia, Guillermo - Elhuyar Zientzia

• Teknologia
• Giza zientziak

Inside and outside fiction, XIX. In London of the twentieth century there were many crimes. In most of the cases that occurred in reality, the author was probably not captured or much investigated. However, in fiction, a detective named Sherlock Holmes dominated the situation and made the criminal known.

Holmes used two weapons, quick head and scientific wisdom. In fact, he spent hours learning in front of the books. In addition, he carried out chemical experiments in the laboratory. For example, he invented in his first story a new method of blood detection (A Study in Scarlet).

Technological detectives technology detectives

In real life, science is also the protagonist in the development of methods of crime resolution. Other areas use the same methodology. The genetic study to confirm fatherhood, for example, can be said to be fashionable. However, such modern methodologies have not left out ancient concepts. When it comes to identifying people, the usual method has been the study of fingerprints. It is currently used frequently.

Each one has its own fingerprints. At first it can be thought that there are no two human beings with identical remains. It is true. However, sometimes the difference is very small and the usual procedure for the study of the tracks is based on a modification of few lines. Lawmakers know this well and on some issues this year the defense lawyers have tried to overturn the test results with this argument. It is not the only problem.

In 1993, a three-year-old girl was kidnapped, raped and murdered in Knoxville (United States) by a family friend. While he was drugged, he acknowledged the crime, but when he recovered he denied it. The police had to search in the car of the suspect the fingerprints of the child, but nothing was found. Arthur Bohanan, a police investigator, discovered why. The footprints of children evaporate rapidly, since the sebum of the hands contains more volatile chemical compounds than adults. Sometimes it disappears in a few hours.

In this field, two lines of research are currently being developed. Some are improving the procedure for identifying people. The objective of another group is to extract most of the possible information from the tracks. The combination of gas chromatograph and mass spectrometer is very useful in these cases.

Fingerprints have traces of the owner's sexual hormones. It can be clarified if the footprint is male or female. In the first case, testosterone and in the second, estrogen. Smokers leave traces of the metabolites of nicotine (and also of cocaine, etc.) ).

Another aspect of this study is the collection of samples, method of collection of the footprint. The tracks can be easily collected from very smooth and clean surfaces. It is almost indispensable that there is not much time since his abandonment. In the long term, traces evaporate or degrade. In general, in the technique used, the footprint is covered with dust and the image is obtained. The other way that is frequently used is to fix the traces with the vapors of the adhesive (cyanoacrylate) to make them visible. The result can be observed with high energy blue light. But this trick is not always useful, it does not give good results in dry and warm places.

The problem that may be behind these techniques is to find more than one footprint on a single piece of skin. In addition, they can belong to more than one person. This type of separation is also being investigated in the criminology laboratories.