FARGO - Lawyers in the trial of the man accused in the death of a University of North Dakota student took a break from jury selection to argue whether DNA evidence was handled properly in the crime lab.

Alfonso Rodriguez Jr., 53, a convicted sex offender from Crookston, Minn., is charged with kidnapping resulting in the death of Dru Sjodin. He has pleaded not guilty.

The hearing on DNA evidence was held Friday, after defense attorneys asked that some of the exhibits be thrown out before testimony begins. The defense motion also asks U.S. District Judge Ralph Erickson to dismiss the case because "the government will rely on its forensic DNA evidence to carry its burden."

Defense attorney Robert Hoy said scientists with the Minnesota Bureau of Criminal Apprehension made a mistake by testing some samples when they knew the procedure would destroy the evidence. That left defense experts with nothing to examine, he said.

Ann Marie Gross, a forensic scientist with the Minnesota BCA, said she followed a "scientifically sound practice" when she opted to test samples without first splitting them in half. At least one of the samples in question was a droplet of blood the size of a dot from a ball point pen, she said.

"If you try to cut something like that in half, physically I don't know how that's possible," she said.

Defense witness Dean Stetler, a biological sciences professor at the University of Kansas, said that based on forensic reports he read, there was enough DNA to split the sample before it was tested.

Later, under questioning from Hoy, Gross said it would have been "possible" to divide the sample, "but based on my experience, I think I took the right approach."

Prosecutors said defense attorneys declined an invitation to have their expert present while tests were conducted. Gross told Hoy that a defense representative would not have been allowed to test or correct any possible errors.

"So that person would be there only as a learned observer?" Hoy asked.

"Yes," Gross said.

Hoy ended his cross-examination by asking Gross about sending "empty envelopes and naked swab sticks" to a defense forensic scientist. Gross said she sent out the samples that were requested.

Erickson said that even if some of the evidence was not handled correctly, defense attorneys still have to show whether the government acted in bad faith.

The judge said he would rule in the defense motion in the next few days, telling lawyers he realized it "was a matter of pressing concern as you prepare for trial."

Jury selection in the case is expected to last at least another two weeks.

Before Friday's testimony, Erickson told lawyers and witnesses to refer to evidence by numbers because some potential jurors did not receive instructions to avoid media reports about the case.

Prosecutors have said they would seek the death penalty if Rodriguez is convicted.