1) A small, circular DNA molecule located in the mitochondria that contains approximately 16,500 nucleotides in humans; the abundance of hundreds of copies of mtDNA in each cell makes it useful with samples originating from limited or damaged biological material. 2) Extranuclear, double-stranded DNA found exclusively in mitochondria that in most eukaryotes is a circular molecule and is maternally inherited. (OSAC Crime Scene/Death Investigation Committee)