Silent Witness - Volume 5, Number 2, 2000

Mitochondrial DNA Evidence Continues to Gain Ground in the Forensic Community

by Kim Herd, Program Manager and Adrianne Day, Legal Intern, APRI's DNA Forensics Program

In the ever-evolving field of forensic DNA evidence, prosecutors are turning to mitochondrial DNA1 (mtDNA) testing in an increasing number of criminal prosecutions. Thus far, trial courts in 17 states have admitted mtDNA evidence.2 Appellate courts in Tennessee, North Carolina, and South Carolina have affirmed trial court decisions admitting mtDNA evidence.3 In January of 2000, a Maryland appellate court will consider a trial court's admission of mtDNA evidence in a double homicide case.4 Forensic laboratories are slowly integrating mtDNA testing into their DNA repertoire. Mainstream acceptance of mtDNA evidence by the judicial system is not far behind.

The rise of mtDNA testing in the field of forensics means that cases that were previously thought hopeless, may now be resolved. Mitochondrial DNA in human cells is often more robust and more plentiful than nuclear DNA. Thus, mitochondrial DNA can frequently be found in biological specimens that are very small or extremely degraded. MtDNA typing can be performed on hair shafts, bone, and teeth. As a result, mtDNA testing has been widely utilized by investigators in "cold case" police units.5 These units use modern technology to establish leads in old cases where traditional investigative techniques have failed.

In spite of the fact that mtDNA is an extremely useful identification tool, there are limitations on the technology. For example, mitochondrial DNA testing is not as discriminating as testing procedures that type the DNA found in the nucleus of cells. In fact, mtDNA testing cannot usually distinguish between people that are related maternally. Despite this limitation, the leader in forensic mtDNA testing, the Federal Bureau of Investigation (FBI), is being inundated with mtDNA testing requests. As of December 1999, the FBI had testified in 21 criminal cases involving mtDNA in the United States, Australia, and Canada. The FBI Laboratory primarily analyzes cases that were submitted by federal investigators, but will also perform mtDNA testing for state law enforcement under certain guidelines. According to Dr. Joseph DiZinno, Chief of the FBI's Mitochondrial DNA Laboratory Unit, (DNA II Unit), prosecutors in non-FBI cases seeking mtDNA testing must first get on a six-month waiting list.6 Once the waiting period passes (and if the need for testing is still there), the prosecutor can submit the evidence samples to the FBI for mtDNA testing. Another federal laboratory, the Armed Forces DNA Identification Laboratory (AFDIL) of the Armed Forces Institute of Pathology "will accept cases from civilian agencies for educational purposes, quality assurance, and/or in cases involving a Federal interest."7

In addition to the FBI and the AFDIL, the following private laboratories also perform mtDNA testing for state prosecutors: LabCorp in Burlington, North Carolina; Mitotyping Technologies LLC in State College, Pennsylvania; Bode Technology Group in Springfield, Virginia; Bio Synthesis Incorporated in Lewisville, Texas; and Relia Gene in New Orleans, Louisiana.8

Prosecutors seeking more in-depth information about the underlying science of mtDNA typing may wish to consult a recent article published in the Forensic Science Review.9 The article describes the sequence and structure of mtDNA in detail and explains concepts such as heteroplasmy and mutation. The article also discusses statistical issues in mtDNA typing and describes the techniques laboratories have used to validate this type of DNA testing.

1 Mitochondrial DNA comes from the Mitochondria found outside the nucleus of the cell and is passed along the maternal blood line.

2 Those states are Alabama, California, Connecticut, Florida, Georgia, Hawaii, Indiana, Louisiana, Maryland, Michigan, New Mexico, North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, and Texas. FBI Laboratory, Selected mtDNA Case Summaries: 1996-Present (1999) (on file at American Prosecutors Research Institute). See Pennsylvania v. Rorrer, PICS Case No. 98-0320 (Lehigh Co. 1998); Pennsylvania v. Dillon, CC# 97-CR-1575 (Lackawanna Co. 1998); Connecticut v. Pappas, CC# CR10-246884 (New London 1999); Florida v. Bolin, CC# 90-11832 (13th Judicial D. 1999).

3 See State v. Ware, 1999 WL 23359 (Tenn. 1999); State v. Scott, 1999 Tenn. Crim. App. LEXIS 758 (1999), State v. Underwood, 518 S.E.2d 231 (N.C. 1999), State v. Council, 515 S.E.2d 508 (S.C. 1999).

4 See Maryland v. Williams, CC# K-94-1073 (Anne Arundel Co. 1998).

5 See Dave Cunningham, The Cold Squad Gets Hot: A New Vancouver Police Unit Cracks Old Murder Cases with New Technology, British Columbia Report at 31-32 (Apr. 13, 1998); Paul Hammel, Team's Hot on the Trail of Cold Cases -- First Two Cases Under Consideration, Omaha World-Herald at A1 (Oct. 17, 1999).

6 Telephone Interview, Dr. Joseph DiZinno, Chief, Federal Bureau of Investigation's DNA Analysis Unit II (Dec. 21, 1999).

7 Armed Forces DNA Identification Laboratory, AFDIL ... DNA Services, <http//:www.afip.org/oafme/afmi.html> (last updated Oct. 22, 1999).

8 Contact information for these laboratories is as follows: (1) AFDIL DNA Services -- 301-319-0210 or www.afip.org/oafme/dna/outsidedna.html (contains a case request form and fee schedule). (2) LabCorp -- (336) 584-5171 or www.labcorp.com; (3) Mitotyping Technologies LLC -- (814) 861-0676; (4) Bode Technology Group -- (703) 644-1200 or www.bodetech.com; (5) Bio Synthesis Incorporated -- (972) 420-0222 or www.biosyn.com, and; (6) Relia Gene -- (504) 734-970.

9 M.M. Holland and T.J. Parsons, Mitochondrial DNA Sequence Analysis -- Validation and Use for Forensic Casework, 11 Forensic Science Rev. 21 (1999).