The method of DNA identification, like the use of fingerprints, is the result of an accidental discovery that arose as a byproduct of other research.
In September 1984, British geneticist Alec Jeffriesaccidentally discovered unique sequences of nucleotides in the DNA chains of different individuals while researching a new method for detecting genetic abnormalities in chromosomal DNA in the University of Leicester laboratory. While analyzing the DNA that codes for myoglobin, Jeffries noticed a series of minisatellites in the gel, where DNA fragments move in an electric field depending on their size. During his research, he discovered that different individuals have different minisatellite sequences. Jeffries understood that this was of great importance. Each person’s DNA sequences form their DNA profile, or “genetic passport,” which can be used to reliably identify an individual. These DNA particles he discovered are unique.
After the publication of the results of his research, Jeffreys was approached by scientists from the British Home Office: they saw in the discovery a reliable way to verify the veracity of the statements of immigrants who claim to have close family ties to British citizens.
The first case in which genetic testing was used was the rape and murder of two girls in November 1983 and July 1986. This new method first helped establish the innocence of the detained Richard Buckland, and then expose the real killer – Colin Pitchfork.

Although 99.9% of human DNA sequences match in composition, the DNA of different individuals is quite individual. In the process of compiling a DNA profile, the number of repetitive elements in the selected genome fragment is analyzed. The repeated element is called a tandem repeat, and its number is variable. The more fragments of the genome (or loci) analyzed during DNA profiling, the higher the accuracy of the person’s identification. Currently, the number of loci for DNA profiling reaches 16 or more.
Compilation of a DNA profile of a person (DNA profiling) should be distinguished from the complete decoding of his genome.
The DNA profiling process begins with the preparation of an individual’s DNA sample (usually called a “control sample”). The most preferred method of control sample collection is the use of a buccal (cheek) scraper, as this reduces the possibility of its contamination. If this method cannot be used (for example, if the procedure requires a court order that does not exist), other methods can be used to collect samples of blood, saliva, semen, or other suitable fluids or tissues from personal items (for example, dental brushes, razors, etc.). Specimens from repositories (such as a sperm bank or tissue biopsy repository) can also be used. Samples obtained from the blood of biological relatives can serve as an indicator of an individual’s profile, as can human remains that have previously been profiled.
The control sample is then analyzed to create a DNA profile of the person using one of the methods that will be described in later articles. Once the analysis is done, the DNA profile can be compared to another sample to determine if there is a genetic similarity.
Meanwhile, the comparison of DNA samples, especially in criminal investigations, may not be sufficiently objective, especially when experts receive additional information about suspects.