In his DNA, every individual presents a specific code that defines his genetic "fingerprint". In fact, with the exception of monozygote (identical) twins, whose DNA is perfectly identical, the genetic profile of every individual, like his fingerprint, is practically unique. This characteristic serves as the basis of the methodology utilized to determine if two persons are genetically correlated.

The paternity test is based on the principle that every individual inherits his genetic patrimony from his parents, 50% from his father and 50% from his mother. The test consists in comparing the genetic characteristics of the child under study with those of the presumed father and mother. To be considered the biological father, the presumed father must possess half of the genetic profile present in the child.

Paternity is EXCLUDED when the genetic characteristics of the presumed father are different from those of the child. Paternity is, instead, ATTRIBUTED when the genetic characteristics of the father and the child are the same.