[Recent developments of genetic markers in legal practice].

The human identification in forensic science is currently based upon the study of highly polymorphic systems with mendelian transmission: the STRs (Short Tandem Repeats). These genetic markers are three to seven bases repetitive sequences spread all over the genome. They are detected by using the Polymerase Chain Reaction (PCR). This analysis method makes it possible to amplify several different loci from very low quantities of genomic DNA (Desoxyribonucleic Acid) in very short periods of time without using any radioactive substances. Interpretation of the results is simple because the amplified fragments are of a known size. The alleles known in each system with discrete values allow the calibration of the revealing gel and the populations studies; moreover, they may be entered into a database. The fragility of this test implies specific precautions with the Laboratory's organization in order to avoid any kind of contamination. Both the establishment of a quality assurance responding to the ISO 9002 standard together with internal quality controls would ensure that these tests are reliable and repeatable in the opinion of the Courts. Only authorized laboratories may perform DNA testing on the occasion of legal proceedings.