DNA experts duel on second day of Aguirre trial

It was a day of dueling experts on Wednesday, the second day of Richard J. Aguirre’s second trial for third-degree rape and fourth-degree assault in Franklin County Superior Court.

The former Pasco police officer is accused of sexually assaulting a woman in November 2014 while she was staying at this home. He denies it happened.

One of the main pieces of evidence against Aguirre, 52, is DNA allegedly found on the victim’s underwear by the Washington State Crime Lab.

Washington State Patrol forensic scientist Ethan Smith said the genetic material along the outside seam of the underwear was 19 trillion times more likely a combination of Aguirre’s and the victim’s than anyone else.

Defense Attorney John Henry Browne had told the jury during opening statements that the amount of DNA found, about 5 nanograms, could have come from anywhere.

Donald Riley, the Ellensburg-based DNA expert testifying on Aguirre’s behalf, agreed. A touch should leave 40 to 50 nanograms, and if someone licked a piece of cloth, tests should find more than 100, he said.

“(The amount of DNA found) is in the range of low level contaminates,” he said.

Riley compared DNA to water, saying it can pass through cloth.

“There’s not much of a barrier between my skin and the last person’s DNA that was sitting here,” he said.

Smith, the state patrol forensic scientist, responded that he had plenty of DNA to get a good sample from the 1-by  1/2 -centimeter section of cloth.

“We usually target between one and two nanograms of DNA,” Smith said. “When we say a trace, it indicates a really small amount ... anything that is under a nanogram.”

He disagreed that licking a piece of fabric would consistently leave a certain amount of DNA.

It’s possible little of Aguirre’s DNA was on the bed at all, Smith said.

Part of the dispute between the experts involved a chemical known as amylase. The enzyme, normally found in saliva, helps break down starches. Smith tested the underwear for it.

Riley testified that the enzyme is found in any number of bodily fluids, including urine and feces.

Smith agreed that the test doesn’t confirm the presence of saliva.

“But the fluids that I have seen that cross-react with that test are fecal material, and, oddly enough, breast milk, and ... there is still much higher concentrations of amylase in saliva,” he said.

Closing arguments in the trial are expected Thursday afternoon.

This story was originally published March 22, 2017 at 7:28 PM with the headline "DNA experts duel on second day of Aguirre trial."