In criminal proceedings, defense attorneys occasionally attempt to establish that a suspect was not present at the commission of a crime by comparing the suspect' s DNA to the DNA of blood or hair samples taken from the scene of the crime  Although every person' s DNA is unique, DNA tests often fail to distinguish among DNA samples taken from distinct individuals
Hence, it is a mistake to exonerate a suspect simply because that person' s DNA did not match the DNA samples taken from the scene of the crime
It relies on experimental data derived from DNA testing that have not been shown to hold under nonexperimental conditions.