FBI special agent Michael A. Vick, exuding utter calmness and confidence, tried to walk the jury through the process of how to link semen found on the body of a murder victim to the blood of a suspect.
On the other hand, defense attorneys representing Daniel Eugene Turner, 32, of Aberdeen in his first-degree murder trial tried to make Vick's DNA evidence sound as complicated as possible.
Vick, an expert in the analysis of DNA, or the material in human cells that determines genetic makeup, was testifying yesterday in the trial of Turner, who is accused of the fatal stabbing of Spec. 4 Bonnie Sue Joseph, 21, an Aberdeen Proving Ground soldier. His testimony is seen as critical to the prosecution's case, which is expected to last at least through tomorrow.
Joseph I. Cassilly, the Harford County state's attorney, is alleging that Turner, a one-time circus laborer, attempted to rape Joseph before stabbing her 25 times on March 12, 1990.
Joseph was abducted from a 7-Eleven early that day after she had left the proving ground to buy cigarettes and food for her and her co-workers.
A conviction on charges of attempted rape, kidnapping or robbery, in addition to murder, would allow Cassilly to proceed with a separate death-penalty proceeding against Turner.
The case, being heard in Baltimore County because of pretrial publicity, is the first involving DNA evidence to come to trial in Harford. It is one of only several death-penalty cases in Maryland to involve DNA.
Vick tried to keep his explanations for the jury simple and direct, comparing the structure of DNA to tangled strands of spaghetti at one point.
Then came several hours of cross-examination by defense attorney Robert Winkler, who forced Vick to explain nearly every step in the six- to eight-week process of analyzing DNA, or deoxyribonucleic acid.
"What's a dilution? . . . Is that an organic compound? . . . So you put four microliters in the gel and you hold out the rest?"
Throughout Winkler's cross-examination, Vick kept his composure, sometimes using an overhead projector or a large drawing pad to make a point.
The upshot of his tests: There is one chance in 700,000 that another black person would have the same DNA "profile" as that found in semen on Joseph's shirt and pants and a blood sample taken from Turner.
But, Vick conceded, "it's not an absolute exclusion." He added that the chance of another person exhibiting the same traits in DNA was only a "theoretical" possibility. Except for identical twins, a person's molecular structure of DNA is thought to be unique, he said.
Winkler, in cross-examination, also attempted to show that the FBI laboratory in Washington and private laboratories around the country have different methods of analyzing DNA. The FBI began DNA analyses in 1988, shortly after a couple of private companies began offering the service to police agencies.
Turner, whose clothes were soaked with blood when he was captured about three hours after the victim was found, has not always kept his composure during the trial.
Defense attorneys have not yet said whether Turner will take the witness stand in his own defense.