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RENO, Nev. (AP) - James Biela cried and told his girlfriend, "I am sorry for everything I've done," after he was arrested on charges of rape and murder, according to a videotaped meeting shown Wednesday to jurors.

The woman - the mother of Biela's child - cried hysterically at times during the encounter, which was arranged and taped by police investigators shortly after Biela's arrest in 2008.

Biela, 28, a former Marine and pipe fitter, is charged with raping and killing 19-year-old Brianna Denison in 2008 and sexually assaulting two other women in 2007 near the University of Nevada, Reno. He faces a possible death penalty if convicted of murder.

The video capped a dramatic day of testimony in Washoe District Court.

Denison was sleeping on a friend's couch when she was abducted in the early hours of Jan. 20, 2008. Her body was found about a month later in a vacant lot in a south Reno business district. Police said she had been raped and strangled.

Earlier Wednesday, Scott Ferris, a manager at EE Technologies, testified that a "pale and shaking" co-worker came across Denison's body in a vacant lot about a month after she vanished while sleeping on a couch at a friend's house.

Ferris said he went with that co-worker, Alberto Jimenez, back to the scene and then called 911.

Authorities said Biela, who was trained in martial arts, had worked briefly at EE Technologies and was familiar with the area where Denison's body was found lying in a shallow ditch and covered by a discarded Christmas tree.

Tucked beneath one of her legs were two pairs of intertwined thong underwear, one of which belonged to K.T. Hunter, the friend Denison was staying with when she disappeared, and which contained DNA from Hunter, Denison, and Biela.

Dave Jenkins, lead detective on the case for Reno police, on Wednesday described how investigators received thousands of tips and spent weeks months interviewing known sex offenders and obtaining voluntary DNA samples from anyone who came to their attention. The DNA tests were used to eliminate them as suspects.

Their big break came 10 months later from an anonymous tipster who said Biela's girlfriend confided in her of finding women's thong underwear in Biela's truck when she went to visit him in Washington state. Biela had left town shortly after Denison's body was found.

Jenkins said Biela was kept under surveillance, and investigators interviewed his girlfriend, who consented to allowing a DNA sample be taken from their son.

From that, forensic experts determined the child's biological father could not be ruled out as the source of the DNA evidence gathered from the Denison and sex attack crime scenes.

Investigators then obtained a seizure order from a judge to take a sample from Biela. An arrest warrant was issued when his DNA matched samples from the crime scenes, Jenkins said.

Biela was arrested Nov. 25 when he arrived to pick his son up from preschool in Reno.