FORENSIC SCIENCES Forensic Mitochondrial DNA Analysis: Two Years of Commercial Casework Experience in the United States

Aim. To describe mitochondrial DNA (mtDNA) forensic casework experience in a commercial laboratory in the United States. Methods. Frequency statistics were kept for two years on all aspects of mtDNA forensic cases, including types of clientele, types of samples, levels of sample success and failure, site heteroplasmy, length heteroplasmy, contamination, rates of failures to exclude, and match statistics using a mtDNA sequence database. Results. Low sample failure rate was observed, especially since an “ancient DNA” approach was used for samples with degraded DNA. Levels of contamination were low, and the observed site and length heteroplasmy did not confound the interpretation of results. The data collected from mtDNA haplotypes developed in casework showed extremely high diversity of haplotypes consistent with other formally developed databases. Conclusions. MtDNA forensic analysis in the private sector was successfully applied to many different types of samples overall, with minimal rates of complication due to sample handling challenges (degraded DNA, minimal samples, contamination) and sequence-specific phenomena (site and length heteroplasmy).