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RENO, Nev. (AP) - Prosecutors said Wednesday that a man with a fetish for women's thong underwear escalated from rapist to killer, with the sexual assaults of two women in 2007 near the University of Nevada, Reno and the death of a college coed in 2008.

In his opening statement to a seven-man, five-woman jury, Deputy District Attorney Chris Hicks said James Biela "graduated from serial rapist to murderer," and that after DNA and other forensic evidence is presented, jurors will reach the inescapable conclusion of his guilt.

But Public Defender Jay Slocum urged jurors not to view the evidence with sympathy or anger, but the "cold light of reason." He said DNA evidence was not conclusive, and that while authorities say they've linked the three crimes to a single assailant, each has "very distinct facts" that shed doubt on the prosecution's theory.

Biela, a Sparks pipe fitter who trained in martial arts, is charged with three counts of sexual assault and one count each of kidnapping and murder. Prosecutors intend to seek the death penalty if he is convicted.

Brianna Denison, a 19-year-old who grew up in Reno, was visiting family and friends during the winter break when she disappeared while sleeping on a couch at a house near UNR in January 2008. A sophomore at Santa Barbara City College in California, her body - covered by a discarded Christmas tree and wearing only socks - was found three weeks later in a snowy vacant lot in a business district in south Reno.

Tucked beneath one of her legs was two pair of women's thong underwear. One belonged to the friend Denison was staying with the night she disappeared, and forensic experts believe it was used to strangle her, Hicks said.

Biela, 28, also is accused of raping a woman in a UNR parking garage at gunpoint in October 2007. Another woman was kidnapped two months later from outside her apartment near UNR and driven to a parking lot where she was assaulted before her attacker drove her home and told her not to call police, authorities said.

In both of those crimes, Hicks said, the women were attacked from behind and the assailant kept their underwear.

The first woman threw away the clothes she was wearing and didn't report the crime until after Denison's abduction, but after his arrest she identified Biela as her attacker.

The second woman, an exchange student who's native language is Mandarin, was the first witness called Wednesday, and told jurors how she was grabbed from behind by an attacker who covered her mouth and choked her to unconsciousness. When she came to, she was forced to perform sexual acts.

The attacker then drove her home.

Biela was arrested in November 2008 after an anonymous tip that led authorities to his ex-girlfriend, who confided to a friend of finding two pair of women's thong underwear in his truck.

Police later matched his DNA to that found on Denison's body.

The trial before Washoe District Judge Robert Perry is expected to last about three weeks.