Both methods were approved by the state's Commission on Forensic Sciences and the DNA Subcommittee, made up of geneticists and scientists who review protocols. A spokesman for the commission said the agency has received the letter from the defense attorneys, but could not comment yet on whether an investigation would be launched. Explore further: Critics worry 'junk science' to reign as forensic panel ends
Recent innovations have included the creation of primers targeting polymorphic regions on the Y-chromosome ( Y-STR ), which allows resolution of a mixed DNA sample from a male and female or cases in which a differential extraction is not possible. Y-chromosomes are paternally inherited, so Y-STR analysis can help in the identification of paternally related males. Y-STR analysis was performed in the Sally Hemings controversy to determine if Thomas Jefferson had sired a son with one of his slaves. The analysis of the Y-chromosome yields weaker results than autosomal chromosome analysis. The Y male sex-determining chromosome, as it is inherited only by males from their fathers, is almost identical along the patrilineal line. This leads to a less precise analysis than if autosomal chromosomes were testing, because of the random matching that occurs between pairs of chromosomes as zygotes are being made.