“I—still—”
“You don’t know whether some blood evidence was trampled away before you got there, do you?”
“No.”
“You don’t know whether one of the spectators bled on the bodies before you got there.”
“I think that’s highly unlikely.”
“But the fact is, you don’t know.”
“I don’t know what happened before I arrived, no.”
“So it’s possible that the blood evidence was contaminated before you arrived.”
“Objection!” Bullock said. “Anything’s possible. This doesn’t aid the jury.”
“Your honor,” Ben said, “this witness’s entire testimony is just a tissue of possibilities. I’m trying to make sure the jury understands all the possibilities he didn’t tell them about.”
Judge Hart’s eyes lit up. “I think he’s got you there, Mister Prosecutor. I’ll allow the question.”
Ben re-asked it. “Is it possible the blood evidence was contaminated before you arrived?”
Camilieri frowned. “I can’t rule it out.”
“Thank you. No more questions.”
For once, Ben sat down happy. Two witnesses in a row had gone well for him, or so it seemed. But he knew he couldn’t let himself rest easy. Yes, two witnesses had gone well, he told himself, but for all he knew, the next one could be a disaster.
As it turned out, he was right.
Chapter 51
BULLOCK AND THE REST of the prosecution team were late returning from lunch. Apparently a big strategy powwow had taken place, a development that Ben found distinctly heartening. Normally Bullock coasted through a trial with an unruffled sense of aplomb; this development suggested that just this once he was a tiny bit worried. Like Ben, he must’ve felt that the defense had effectively dealt with the first two prosecution witnesses of the day, and he was concerned.
Good.
On the other hand, of course, as Ben knew quite well, when Bullock felt it was time to pour on the pressure, he knew how to do it. But there was no way to anticipate that. All he could do was stay alert and wait for the other shoe to drop.
“The State calls Dr. Stafford K. Regan to the stand.”
Goodness, Ben thought. Not only an honorific but a middle initial. He must be an important witness indeed.
Dr. Regan took the stand. He was younger than one might guess, trim and handsome and athletic. Obviously not someone who had spent his entire life gazing out from behind the test tubes. In fact, as Ben already knew, Regan’s specialty was DNA analysis. Ben supposed it was only natural that the DNA expert would be on the young side. As in the case of computers or any other emerging science, it was the next generation that took the lead.
Bullock led Regan through a succinct accounting of his background and credentials. He was in fact a medical doctor, but had chosen to pursue research rather than practice. For the last four years, he had been at the Cellmark facility in Dallas, where he not only received a salary but had a small ownership interest. His current title was vice president of research and analysis.
“Dr. Regan,” Bullock asked, “how did you become involved in the present case?
“I was contacted by a member of the Tulsa County district attorney’s office,” he answered. He seemed calm and self-assured. Someone you’d want your daughter to marry. And, Ben thought, unfortunately, not someone who was likely to crumble under cross-examination. “A woman named Myrna Adams.”
“Why did Ms. Adams contact you?”
“She was working on the prosecution team for this case, investigating the murders of the three Barrett family members. They had a few unmatched blood traces, and also, the coroner had found some skin tissue that they believed might be susceptible to genetic testing.”
“Do you know where this skin tissue came from?”
“Yes. The coroner found it under Mrs. Barrett’s fingernails.”
“How did you respond to this inquiry?”
“Well, I was concerned about whether they would have sufficient material to conduct accurate testing. So I asked her to have the genetic materials forwarded to my office.”
Bullock paused, glanced up at the jury. “Before we go any further, Doctor, perhaps I should ask you to explain to the jury just what DNA is.”
Regan nodded, and following his cue, turned to face the jury. “Human chromosomes are made up of deoxyribonucleic acid—what we call DNA. It’s found in the nucleus of human cells. DNA is a highly complex, two-stranded molecule wound into a double helix—sort of like a spiral staircase.” He wove his hands around one another in demonstration. “These strands are made up of some three billion chemical units, each of them representing one of the four letters in the genetic code. The chemical components of the DNA strand have a certain sequencing, sort of like if you threw letters of the alphabet up in the air and watched them fall back into place. Most of the sequence is the same in all humans, but there are variations, particularly in what we call the ‘junk’ stretches of DNA between the genes, where triplets of code letters are repeated over and over again. It is the sequence and number of these components that becomes a blueprint for the inherited traits that make each of us what we are.”
“Thank you, Doctor.” Bullock made a small, probably meaningless notation on his outline. As he had told Ben many times, when the experts go into their lecture mode, it was best to take things slow and easy. The last thing you wanted was a panel of confused, glassy-eyed jurors. “Where can this DNA be found?”
“DNA can be extracted from almost any living tissue. Blood, semen, saliva, hair. And as I mentioned, skin.”
“And what is the value of this DNA analysis?”
“Well, that’s probably already obvious.” He smiled slightly. Never hurts to flatter the jurors. “Once you’ve determined a DNA sequence from trace evidence found at a crime scene, you can compare it against a sample taken from a suspect to see if it matches.”
“Thank you, Doctor. Now let’s return to the case at hand.” Ben saw the jurors almost imperceptibly inch forward as the conversation moved from incomprehensible genetic science to very understandable high-gloss murder trial. “Did you in fact do any DNA analysis of the samples found at the Barrett crime scene?”
“Yes. There was sufficient material in the blood samples for what we call RFLP testing, and although the skin traces were very small, there was enough to conduct what we call PCR tests. They are both highly reliable DNA tests.”
Uh-huh. Ben started making notes. He knew this would be important later.
“What’s the difference between the two, Doctor?”
“Well, without getting overcomplicated, the RFLP stands for restriction fragment length polymorphism.”
Oh, well, Ben thought, thank you for not getting overcomplicated.
“This test requires more genetic material, which is why we used it only on the blood. It involves a complicated process of radioactively photographing the DNA bands on X-ray film.”
“And the other test procedure?”
“That’s the PCR—for polymerase chain reaction. For that, we don’t need any more genetic material than would fit on the head of a pin. It’s a sort of genetic Xeroxing. Individual genes are copied millions of times to form a composite picture—a series of blue dots, actually—that can then be tested for common chemical sequences.”
“Would you explain just how these tests are conducted, Doctor?”
“Certainly.” Regan turned toward the easel as Bullock mounted several more enlarged charts illustrating the DNA analysis process for the doctor to use as visual aids. “I’ll use the RFLP procedure by way of example. First, we extract the DNA from the sample, in this case the blood. Then we expose the DNA to enzymes that recognize certain sequences of code letters and snip the strand at those sequences, thus cutting the DNA into fragments of varying lengths.”