Human Mitochondrial DNA

In some situations, human mitochondrial DNA may be the only form of forensic typing possible. Mitochondrial sequencing of the control region can provide significant information which may assist in resolving issues in a criminal case, even though the frequency information provided is substantially less discriminating than with other forms of DNA typing. Other technical issues have arisen which also serve to limit the amount of discriminating information provided by this approach. For example, it has been documented that different samples from the same person may produce sequences that differ slightly.23 To accommodate this phenomenon, interpretation guidelines have been developed to ensure that courts can have confidence in results produced by this technology.24

While the profile frequency is much less discriminating with mitochondrial DNA than that produced by other forms of forensic DNA typing, in the context of any investigative scenario the results may nevertheless be as persuasive to a jury as a profile frequency match between samples of one in a trillion. The following summary of a murder case illustrates this point. The four-year-old female victim was left in the care of a friend while her mother made the rounds of local bars. She was found lifeless early the next morning: the cause of death was asphyxiation. In addition, she had been raped and sodomized. No biological evidence of sexual assault was found in or on the victim's body. During the autopsy, a foreign pubic hair was found in the victim's pharynx and subjected to mitochondrial DNA typing. The hair mitochondrial DNA sequence compared favorably to defendant Ware's known sequence. That sequence had never been observed in any of the 742 samples previously typed and catalogued in the Federal Bureau of Investigation's (FBI's) database (State v. Ware25). In the context of the rest of the evidence against Ware, the mitochondrial DNA evidence helped convict him of first-degree murder.

More recently, another court reviewed the admissibility of human mito-chondrial DNA; Magaletti v. State26 involved a murder prosecution in Florida. Defendant's fingerprints were found on the inside of the victim's door underneath the door knob. Microscopic and mitochondrial analysis of a hair adhering to bindings on the victim associated the hair to the defendant, not the victim. In upholding the trial court's decision to admit the DNA typing results, the Court attached significance to the fact that ". . . the counting method is the only method of reporting used by analysts in the United States." (Maga-letti v. State, p. 526) This statement recognizes the importance of reaching consensus for the admissibility of scientific testimony. Florida is a Frye jurisdiction, but this decision relied on decisions from other states, some of which utilize the Daubert standard.

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