CHAPTER 65
The following morning, with the sun poking through the low-hung sky for the first time in two weeks, Denton called Dr. Leonard Ross to the stand. Dr. Ross, a researcher well schooled in the analysis and typing of DNA, had written a textbook on the topic. As a witness he was presentable, though he did have a tendency to talk above the heads of the jurors at times. At two thousand dollars for a half-day of testimony, Denton wanted to make sure Ross’s message got through loud and clear to the jurors; he met with his witness on two occasions to go over the testimony and ensure the fact that the words he used were no more than three syllables in length.
Ross testified as to what the prosecution wanted to communicate to the jury: that the evidence was properly handled and preserved with little or no risk of contamination, and the delay in running the DNA testing was of no consequence whatsoever.
He explained the process of DNA analysis, starting with the protein building blocks and moving through genetics in half an hour in a manner that would have had even a ten-year-old nodding comprehension. Denton was pleased with how it was presented.
Although Warwick pecked away with information supposedly quoted from his own consultant, namely that the delay could have caused degradation and produced incorrect results, Ross stood by his position. He referred to his textbook repeatedly, a tactic that was designed to solidify his reputation as the expert and to ground his opinions in fact. “You’re arguing with the person who wrote the book,” Ross said at one point-which could have been taken as egotistical and turned off the jury. However, it came off instead as his way of defending himself from Warwick’s incessant attack that was riddled with desperation tactics and baseless opinions.
“Answer this for me, sir,” Warwick asked, getting up close to Ross, “why did the lab use the PCR method as opposed to the RFLP method of analysis?”
“PCR is more sensitive. It also allows typing in situations where it wouldn’t have been possible before. It gives us the ability to type DNA with the smallest of sample sizes. All we require is one-billionth of a gram of DNA. Before, we wouldn’t have been able to even begin analysis with RFLP on such a small sample size.”
“PCR…isn’t that the method where photocopies are made of the DNA pattern? Isn’t it less accurate than RFLP?”
“Let me answer one question at a time,” Ross said with a chuckle. “You mention photocopying. That’s a gross simplification to the point of being misleading. PCR is a technique that was developed from the very basis of how DNA strands naturally replicate, or copy themselves, within a cell. The key concept is that an enzyme called DNA polymerase can be stimulated to synthesize, or create, a specific region of DNA. In the same manner, PCR can be used to repeatedly duplicate or amplify a strand of DNA many millions of times. So it’s not photocopying,” he said, talking down to Warwick in a manner in which a teacher reprimands a student who was attempting to show off at the teacher’s expense.
“Now to your other question of PCR being less accurate than RFLP,” Ross continued. “It used to be that the frequency of occurrence of one of the gene types that is isolated, the DQ alpha gene, is greater than the frequencies typically obtained through the RFLP method. But, a typing kit known as Polymarker allows the typing of five different genetic markers. When used in combination with DQ alpha, it will produce frequencies of occurrence of less than one in a thousand. In this case, Mr. Saperstein also included the DIS80 marker, which is quite an uncommon marker.
“In general, the more markers you use, the better the odds are in excluding possible matches from the general population. That’s why the odds in this case are one in fifty thousand.” Ross paused for a second to take a breath. “So, I personally do not feel that anything significant is lost with the PCR method-in fact, a tremendous amount is gained.”
Warwick looked perturbed for a moment. He had committed the cardinal sin in cross-examination: he had asked a question without making sure he knew the answer that was coming. But in fact, there was no way that Warwick could have known that Ross was going to cite cutting-edge research and methodology.
“How big a sample of DNA are we talking about in this particular case against my client?”
“The DNA was obtained from saliva residues on a beer can, so there was more than enough to get an accurate result.”
Denton knew that Warwick was well aware of that very unfortunate fact.
The public defender cocked his head. “How big is a molecule of DNA?”
“It’s microscopic.”
“So it’s nothing we can really see with the naked eye. It’s nothing that I or any of the jurors could look at and see for ourselves.”
“No. But I assure you it exists and is quite real.”
“Uh-huh,” Warwick said, as if to mock Ross’s last comment. “You said earlier while being questioned by Mr. Denton that DNA can become contaminated?”
“Yes.”
“What are some of the ways in which this can occur?”
“A number of factors or situations.”
“Can you name some?”
“Improper handling of the evidence, improper storage conditions, high humidity, excessive dirt, dust, things of that nature.”
“What about sneezing? Could that spoil a sample?”
“Yes.”
“Coughing?”
“Yes.”
“Hmm,” Warwick said, pacing away from the witness.
The jurors’ eyes followed him. “Something as benign as a sneeze could contaminate the sample.”
“Yes, but-”
“And how much time elapsed between the time that the evidence was gathered and the actual lifting of the saliva from the cans?”
“As I said earlier, I believe six weeks.”
Denton felt pimples of sweat forming on his forehead.
“Six weeks,” Warwick said. “And you said dust or even dirt could contaminate the sample?”
“Again, as I said a moment ago, yes. But it would have to be-”
“And when a DNA sample is contaminated, the results that it yields are then no longer considered accurate.”
“I suppose you could say that.”
Warwick had stopped and leaned back against the defense table, arms folded across his chest. He looked hard and long at Ross, as if he were pondering what he had just answered. It was no doubt intended as an exclamation point for the jury. “Yes, I suppose I could. Thank you, Dr. Ross. I have nothing further.”
“Redirect, Mr. Denton?” Calvino asked.
“Yes, Your Honor.” He stood rapidly and walked to the spot in front of the witness stand, facing Ross. “Doctor, was the sample in question contaminated?”
“No. Not to my knowledge.”
“Was the evidence properly stored, in a facility where there were no unusual amounts of humidity, direct sunlight, dust, or dirt?”
“From what I’ve read in the report, standard protocol was followed, and the evidence was properly marked, stored, and handled.”
“How does sneezing or coughing contaminate a sample?”
“Contamination occurs because you have someone else’s DNA intermixing with the sample DNA. It’s only a concern when you’re dealing with a very small sample, which, as I said, is not the case here. However, even if it were, we would be able to separate out the DNA from the person who sneezed or coughed from the DNA of the suspect.”
“It sounds very sophisticated.”
“It is,” Ross said. “Very sophisticated.”
“And accurate?”
“Extremely accurate.”
“If a DNA sample were contaminated or degraded by dirt or dust, or any such substance, would the tainted analysis come back with results implicating Brittany Harding?”
“No, the results would either be incomplete or unmatchable.”
“And that was not the case here?”
“No.”
“They clearly matched Brittany Harding’s DNA?”
“Yes, they did.”
“Is there any reason to believe that the results produced by the DNA analysis in this case were tainted, degraded, contaminated, or otherwise rendered inaccurate?”