Regan pulled out his next chart, then continued his explanation. “These segments are placed in a gel and are subjected to an electrical charge that pulls them down into the gel. The critical factor here is that the short pieces move faster than the longer ones. Therefore, the fragments are separated into a pattern of bands that can then be recorded on X-ray film.”
“Thank you, Doctor. Once you have recorded these patterns on X-ray film, what do you do with them?”
“Then we can make comparisons, such as the comparison I made between the patterns derived from the DNA found at the crime scene and the DNA taken from the defendant. The comparison is actually quite simple; you can literally lay the two X-ray films on top of each other.” Regan moved to the next chart, which was an enlarged photo of him doing just that. “In this manner, it is easy to determine whether there is a match between samples.”
Bullock laid his hands down on the podium. “Dr. Regan, I thank you for making this complicated process understandable. What we all really want to know about, of course, are the results of the tests you made in this case.”
“Certainly.” Regan exposed the final exhibit in his stack. “We compared the DNA samples taken from the defendant while he was incarcerated to both samples taken from the crime scene, using both tests. The blood was subjected to RFLP testing, and the skin was subjected to PCR testing.”
“And?”
Regan looked directly at the jurors. “And in both cases, the DNA from the crime scene matched the DNA taken from Wallace Barrett.”
“In both cases? Both the skin and the blood?”
Regan nodded solemnly. “That’s correct.”
There was an audible stir in the jury box. This was perhaps the most incriminating evidence yet. After all, witnesses could make mistakes, but science never makes mistakes. Or so the prosecution would have them believe.
“Dr. Regan,” Bullock said slowly, “I don’t want to make you repeat yourself, but you have to understand—this is a very important piece of evidence. Is there any possibility that you or your staff could have made an error?”
“None. I either did or supervised the work at every step. We double-checked and triple-checked everything. There was no mistake. The DNA samples match.”
“Very well then. Thank you, Doctor.” Bullock hung his head low and wore a grave expression. “I guess that’s all there is to say.”
Chapter 52
BEN PLANNED HIS CROSS as he walked to the podium. Obviously he would have to attack the methodology and the purported certainty of these DNA techniques, but there was another point to make that was probably even more important. Throughout the direct examination, Bullock had treated Dr. Regan like a member of his staff, like a police lab tech, which of course he wasn’t, by a long shot. That was something that needed to be set straight right off the bat.
“Good afternoon, Dr. Regan,” Ben said.
Regan looked at him warily. Was this a trick question? “Afternoon.”
“Dr. Regan, how much has the State paid you to testify today?”
There was a stir in the courtroom. Ben was pleased to find that Bullock was not the only one who had the ability to do that.
“I… I haven’t been paid for my testimony,” Regan protested.
“But you have been paid.”
“Ye-es.”
“And you are testifying.”
“Ye-es … but I—or rather, my firm was paid for its scientific expertise and professional services.”
“Which include providing a jury-and-camera-friendly witness to testify in court.”
“Objection!” Bullock said.
“Sustained.” Judge Hart looked at Ben sternly. “Counsel, restrict yourself to the relevant matters at hand.”
“Yes, your honor.” He looked back at Dr. Regan. “You’re not a member of the police force or the district attorney’s office, right?”
“That’s correct.”
“You wouldn’t be here, except that they needed a DNA expert, so they paid you to be their expert.”
“Counsel, these scientific procedures are very expensive. The bills have to be paid.”
“I understand that. But when a witness is being paid to testify, I think the jury has a right to know it, don’t you?”
Regan began to get his dander up. “For the last time, I was not paid to testify. We receive a flat fee up front. That fee does not change, regardless of what our findings are.”
Ben continued to push. “So you think the prosecutor’s office would be happy to pay you thousands of dollars even if you couldn’t help their case.”
It was the classic one question too many, as Ben immediately recognized just as soon as it was too late to take it back. “In fact, our DNA analysis more often excludes suspects than it positively identifies them. DNA is a brilliant tool for eliminating suspects. Numerous people in the past few years have been released, even after conviction, when DNA evidence proved they could not have committed the crime.”
Swell, Ben thought. That’s what he gets for talking faster than he could think. “Let’s talk about these purported matches, sir. Are you saying that you examined every single chemical unit of the DNA found at the crime scene and found that they matched every single chemical unit of the DNA taken from Wallace Barrett?”
“No, of course not.”
“No?” Ben turned toward the jury box. “But you told these jurors that they were a perfect match.”
“Matching here is a term of art. You have to understand—a human DNA molecule contains over three billion chemical units. Even if we had the scientific capability of examining every one of those—which we don’t—it would take forever. Instead, we scan a representative sample. If there are no deviations in those samples, we call it a match.”
“Even though it may not be.”
Regan’s face flushed with irritation. “It is a match, counsel. Given the impossibility of examining every single chemical unit.”
Ben continued to push. “But it’s still possible that some of the other chemical units—the ones you did not scrutinize—might not match.”
“It is theoretically possible, yes, but the odds against that happening are astronomical.”
“How astronomical?”
“It’s ridiculous to even contemplate these numbers. The odds of an RFLP DNA match between samples from two different people are one in ten million.”
“Ah, another oddsmaker. The prosecutor should be Jimmy the Greek.” Ben glanced at his notes. “Of course, you only conducted the RFLP test on the blood. The presence of Barrett’s blood doesn’t necessarily make him the murderer.”
“There was also the skin beneath his wife’s fingernails—”
“Yes, but you conducted only the PCR test on the skin samples, right?”
“That’s true. There wasn’t enough material for a RFLP.”
Ben’s eyes raced through his notes. Thank goodness, Jones’s pretrial research had made him something of a DNA expert himself. Otherwise, an effective cross would be impossible. Unless the lawyer educates himself, there is no hope of a successful cross. That’s why scientific experts were so often able to bamboozle lawyers. “And the chances of a match between samples from two different people are much greater on the PCR test, aren’t they?”
“It’s still about four thousand to one.”
“Is that all?” Ben tried to sound incredulous. “Then you could have a false positive.”
“It is theoretically possible. But highly unlikely.”
“Four thousand to one doesn’t sound impossible to me, Doctor. And you haven’t even accounted for statistical skewering due to subpopulations, have you?
Regan tugged at his tie. “Well, no.”