Until the fall of 2007, Michael John Anderson, a socially awkward alternative high-school dropout, used Craigslist mostly to buy and sell truck parts.

But then the teenager who could barely talk to members of the opposite sex suddenly turned to the classified ad website to lure unsuspecting women to his home. He posted at least a dozen ads, some seeking "sexy-voiced women and models," others actresses and babysitters. In late October, he posted an ad purported to be from someone named Amy in search of a "sitter" for a 5-year-old girl.

Katherine Ann Olson responded and showed up to the home in Savage on Oct. 25. The next day she was found dead, stowed in the trunk of her own car.

Anderson's desire for sex was what ultimately led to the accidental shooting of Olson, his defense attorney, Alan Margoles, argued Monday, revealing for the first time a possible motive behind the killing during opening statements at Anderson's first-degree murder trial.

"Remember, Michael Anderson was 19, a dumb kid," Margoles said. "He had no girlfriend ever, he never dated, never went to a high school dance, never held a girl's hand. The evidence will show this guy was too scared of unattached girls to even open his mouth around them."

Anderson's social awkwardness led to the online ads, Margoles said, adding that Anderson lured Olson to the home he shared with his parents "for sex or some odd consequence of romance."

Prosecutors say Anderson lured Olson, 24, to the home with intent to kill, shot her in the back and hid her body in the trunk of her car, which later was found in a Burnsville park. There was no evidence of sexual assault.

Assistant Scott County Attorney Michael Groh used a slideshow to detail the events leading up to the discovery of Olson's body, including how she likely bled to death, alone, wrapped in a sleeping bag in the trunk of her own car. She may have taken up to 20 minutes to bleed to death, Groh said.

"Katherine had undone one of her pearls and clasped it between her fingers before she died," he said.

Anderson, who traded in his green jail jumpsuit for a suit, sat quietly while the jury of eight men and seven women viewed photos of the victim. One showed a smiling Olson, holding one of the children she baby-sat with; another photo showed her body as it was discovered. Some members of Olson's family wiped their eyes.

Margoles never disputed that Anderson shot Olson, but argued that his motives for doing so did not involve thrill-killing, as prosecutors have asserted.

The blatant evidence of Anderson's guilt, his attorney said -- including stuffing a blood-soaked towel with his own name on it in a garbage can and the electronic evidence linking him to the online ads, show the opposite of premeditation, Margoles said.

`"The evidence will show what an 8-year-old would do if he broke a cookie jar," Margoles said. "It will show sexual intent, but not murder."

But Groh said Anderson's actions after the killing showed complete lack of remorse -- if not pride for his actions. When a friend asked why Anderson didn't just plead insanity, Anderson responded with "'Because I'd have to pretend I'm sorry,'" Groh said. "Then he smiled."

In pretrial hearings, the defense revealed that its psychiatrists diagnosed Anderson with Asperger's syndrome, a mild form of autism sometimes characterized by clumsiness and eccentric speech and behavior. The defense argued that the disorder would help explain Anderson's behavior, while the prosecution argued that the claim amounted to a diminished-capacity defense.

District Judge Mary Theisen ruled before the trial began that the defense's argument was insufficient to show that the disorder had anything to do with Olson's death.

The defense lawyer told jurors Monday: "The prosecution will spend day after day after day showing you the evidence that we just admitted." Margoles also said: "High-tech is not a replacement for common sense."

He also warned jurors not to let emotions cloud the facts, the central fact being that Anderson did not premeditate Olson's death.

"You will see terrible images. You will want to close your eyes. You will want to close your ears. Please, don't close your mind," Margoles said.

Two of 57 potential witnesses took the stand in the first day of the anticipated three-week trial. Among them were Savage police officer Joseph Suel, who was among the authorities who found Olson's purse in a trash can at Warren Butler Park in Savage and later her body.

Olson's mother, Nancy Olson of Cottage Grove, also discussed the last time she saw her daughter alive. She was singing in the church choir at Richfield Lutheran Church, where her father, Rolf Olson, is the pastor. Over the next few days, the panicked search for a daughter she described as "like trying to describe a cloud" ended in tragedy.

Chief Deputy Scott County Attorney Ron Hocevar then asked Nancy Olson when she saw her daughter after that.

"In a casket at Morris Nilsen funeral home," she said. "Cold and smelling of chemicals."

Testimony will resume this morning.

Abby Simons • 612-673-4921