Silent Witness - Volume 4, Number 1, 1998

New FBI Policy Revolutionizes DNA Court Testimony

written by Angela Hart, Staff Attorney, APRI's DNA Legal Assistance Unit

The Milwaukee County District Attorney’s Office and the FBI made legal history in a recent Wisconsin double rape trial when for the first time in U.S. legal history a DNA analyst definitively identified the defendant as a rapist based on his genetic profile.

New FBI Laboratory Policy

The FBI Laboratory began performing DNA analysis on evidence submitted in criminal investigations in 1988. In addition to analyzing evidence in federal cases, the FBI also analyzes evidence submitted by state and local prosecutors. Until recently, FBI examiners were only able to testify that individuals could not be excluded as possible sources of DNA evidence. Their conclusions were supported by mathematical probabilities that another unrelated individual in the population had the same DNA type as the evidence.

On October 1, 1997, a new laboratory policy was implemented which enables FBI examiners to state with a reasonable degree of scientific certainty whether an individual is the source of an evidentiary DNA sample. The DNA examiners use Restriction Fragment Length Polymorphism (RFLP) typing to generate the DNA profiles from the known and evidentiary samples at six different genetic loci on the DNA molecule. If the generated profile matches the profile from the evidentiary sample, the matching profile is compared to DNA profiles collected and validated by the FBI from various population groups. Then, the probability of selecting another unrelated individual from the population with a similar DNA profile is calculated. If the probability exceeds one in 260 billion, an identification can be declared with a reasonable degree of scientific certainty and can be testified to in court. This new policy was applied in court for the first time in October 1997 in a Wisconsin double rape trial.

Wisconsin v. Shuttlesworth

Iran L. Shuttlesworth, a 25 year old prison guard, was brought to trial in October 1997 on two counts of kidnapping and four counts of first degree sexual assault for attacks on two young women in Milwaukee, Wisconsin, that took place in November 1995 and January 1996. The case was prosecuted by Assistant District Attorney Norman Gahn of the Milwaukee County District Attorney’s Office.

The two victims positively identified Shuttlesworth as the man who assaulted them. The state also presented DNA evidence comparing the DNA from semen samples recovered from the victims to the DNA from a blood sample of Shuttlesworth. The samples were analyzed by the DNA Unit at the FBI Laboratory in Washington, D.C. using RFLP testing. FBI analyst Dr. Thomas Callaghan testified that the DNA profiles of the semen samples recovered from the victims matched the profile of the defendant Shuttlesworth. Dr. Callaghan further testified that the probability that the DNA profile of the semen sample from the first attack belonged to another person was between one in 1.75 billion and one in 10 billion. The probability that the DNA profile of the semen sample from the second attack was that of another man was between one in 510 billion and one in 9.1 trillion. These staggering numbers permitted Dr. Callaghan, for the first time in U.S. legal history, to identify the defendant Shuttlesworth as the source of the semen in the second attack.

The DNA evidence along with the victims’ identification of Shuttlesworth as the rapist was enough to convince the jury to convict Shuttlesworth on all counts even though the defense presented four defense alibi witnesses, including Shuttlesworth’s wife, a police office for the City of Milwaukee. According to Norman Gahn, the DNA evidence was critical in overcoming the testimony of the alibi witnesses. A survey of the jurors after Shuttlesworth’s conviction indicated that a majority of the jurors thought the DNA evidence presented in the case was very important. The jurors were evenly split, however, over whether the exact match testimony concerning evidence from the second attack was more compelling or equally compelling than the probability testimony concerning the evidence from the first attack.

Shuttlesworth was sentenced to 160 years in prison and will not be eligible for parole until he is 65.

Implications of the Policy

In the future, with the continuous development of new genetic markers for DNA analysis and the addition of more profiles to current population databases, the new FBI policy will be applied in increasing numbers of criminal cases. Jurors may be spared technical and often confusing explanations of population genetics and statistics because DNA examiners will be able to testify to a matching DNA profile without qualifying the match with complicated mathematical probabilities. Furthermore, now that the FBI policy has paved the way for definitive identifications of an individual as the source of an evidentiary DNA sample, other laboratories conducting DNA analysis may soon implement similar policies.

As with any new scientific advance brought into the courtroom, the FBI policy will draw numerous legal challenges. However, because the policy is based on scientifically and legally accepted techniques of DNA analysis and statistical calculation, defeat of these challenges is anticipated.