FORENSIC GENETICS: HISTORY, OBJECT OF STUDY, METHODOLOGY - BIOLOGY - 2025

The forensic genetics is a specialty that uses techniques and knowledge of genetics and medicine to solve legal problems. Currently its main function is the identification of people based on DNA analysis, a molecule that stores all the genetic information of an individual with the peculiarity that it is unique and different for each human being.

Forensic genetics is applied, for example, to carry out paternity tests and, in criminalistics, to determine perpetrators of crimes or identify corpses based on biological fluids or anatomical remains.

Forensic genetics helps to determine perpetrators or identify corpses. Source: pixabay.com

Within the former, samples of blood, semen, urine, saliva, mucus or tears are analyzed. Meanwhile, to examine anatomical remains, teeth, skin, hair, bones or organs are required.

On the other hand, an increasingly important activity within this discipline is DNA databases. In them, the genetic information of criminals, missing persons and unidentified human remains is loaded, which are then used and collated to solve different crimes.

Another relevant aspect of forensic genetics is the standardization of quality control systems in the laboratories responsible for analyzing the samples, to avoid errors and contamination.

History of forensic genetics

The history of forensic genetics began at the beginning of the 20th century when the Austrian biologist Karl Landsteiner managed to identify the four major blood groups (A, B, AB and 0, known as the AB0 system) and showed that transfusions within them were safe.

He then noticed that certain blood characteristics were inherited and, from 1912, this began to be used to confirm paternity in cases where there were doubts. At the same time, this analysis also began to be used to examine bloodstains at crime scenes.

The blood group is a classification made on the basis of the characteristics present on the surface of red blood cells and blood serum. The two most important categories are antigens (the AB0 system) and the Rh factor

Initially, criminalistic investigations focused on the study of erythrocyte antigens (AB0 and MN systems, Rh factor), MN), serum proteins, erythrocyte enzymes, and the human leukocyte antigen (HLA) system.

With these markers, a person could be incriminated or released, for having a genetic combination equal to or not the one found at the scene of a crime.

However, this technique had many limitations when it came to analyzing small or degraded samples, hairs or sperm stains, so it could not be used in most cases.

DNA fingerprinting

Everything changed when, in 1984, British geneticist Alec Jeffreys discovered the techniques of genetic fingerprinting and DNA profiling, which revolutionized forensic medicine.

This method was used for the first time in an illegal immigration litigation and it enabled a child whose family was originally from Ghana to be checked on the British background and thus prevented from deportation.

Then, the following year, it was used to identify a rapist and murderer of adolescents, from semen samples obtained from the corpses of two girls.

Another famous case where this technique was used was to confirm the identity of the Nazi doctor Josef Mengele, who died in 1979, by comparing the DNA obtained from a femur from his corpse with that of his widow and son.

Object of study

The main object of study in forensic medicine are genes. These make up a chain of deoxyribonucleic acid (DNA) that stores genetic information and transmits them from parents to children.

Much of the DNA is similar in all people. However, there are inherited regions that vary from one to another. In this way, by analyzing certain fragments, it is possible to generate a genetic profile of each individual, which is characteristic and unique.

These variations are known as "polymorphisms". Currently, most genetic profiling is performed by simultaneously studying 10 to 17 short regions of DNA, known as Short Tandem Repeats (SHTs).

They are analyzed in laboratories and compared with samples from biological paternity investigation cases and criminalistics expertise. In addition, they are also used to identify corpses and bone remains.

Methodology

DNA stores all the genetic information of a person and is unique and different for each human being. Source: pixabay.com

In criminology, usually the stains, fluids and biological remains are collected at the crime scene and from there they are sent to the laboratory.

With them, the forensic doctors obtain a genetic profile and compare it with the samples of the suspects, obtained by means of a buccal collection with a swab or a blood extraction.

They can also upload the information to a database, to see if there is a match with the DNA of criminals or missing persons or with samples found at other crime scenes.

Advances in forensic genetics and its degree of specification are increasing, allowing the detection of smaller and smaller amounts of DNA.

In the future, it is expected that, from this, it will be possible to predict the physical characteristics of a person and to know, for example, their skin, hair and eye color, and other facial features, which will be very useful during a police investigation.

Difficulties of this methodology

The main difficulties that this methodology offers are contamination and the assessment of evidence. To solve the first, quality standards were created to ensure their control, both when taking the samples and during their handling in the laboratory, but errors are always possible.

Regarding the evaluation of the evidence, it is important to bear in mind that the detection of DNA in a place where an offense was committed does not determine the guilt of a person, so it is essential to analyze the context.

For example, if an individual shakes hands with another, they leave their genetic imprint on them. And if he is later found at a crime scene, the DNA of the person who has never been there can also be found.

In this way, forensic genetics can mark with great precision who a certain sample comes from. But not how it got to the place itself.

This must be carefully analyzed by the courts in charge of administering justice, along with other evidence that defines the guilt or not of a suspect.

References

1. Euroforgen (European Network of Excellence in Forensic Genetics) and Sense about Sience (2017). Interpreting forensic genetics. Available at: senseaboutscience.org.
2. Crespillo Márquez, Manuel and Barrio Caballero, Pedro. Forensic genetics. From the laboratory to the courts. Díaz de Santos editions. Spain.
3. International Society for Forensic Genetics. Available at: isfg.org
4. Carracedo Álvarez, Angel. Forensic Genetics. Encyclopedia of Biolaw and Bioethics. Available at: encyclopedia-bioderecho.com
5. Interpol. DNA. Available at: interpol.int
6. Forensic genetics, Wikipedia. Available at: wikipedia.org