The day before she vanished, Laci Peterson (search) spent what appeared to be a routine day preparing to host Christmas dinner with her family -- she went grocery shopping, visited a local spa and made sure the house was clean.

A series of prosecution witnesses on Thursday reconstructed her comings and goings on Dec. 23, 2002, what authorities say was the last day anyone besides her husband -- and alleged killer -- saw her alive.

Prosecutors have chargedScott Peterson (search) with murdering his eight-months-pregnant wife on or around Christmas Eve day, then driving her body from their Modesto home to San Francisco Bay and dumping it from his small boat. Peterson, 31, could face the death penalty or life without parole if convicted.

While the trial began this week with sweeping claims of his guilt or innocence, it resumed Thursday with mundane details of Laci Peterson's holiday preparations.

Two days before the couple was to host Christmas dinner, Laci Peterson spent nearly $100 at a Trader Joe's grocery store on 24 items, including salmon, eggs, shrimp and soup, according to store employee Fred Eachus.

Just after noon, she went to the Sweet Serenity Day Spa for a waxing treatment, the owner testified.

Unlike many of her other clients, owner Michelle Buer said Laci Peterson never complained about her husband, though she did mention that she was uncomfortable and not sleeping well.

Prosecutors also focused on what Laci Peterson was wearing -- black pants, a white long-sleeved shirt and black shoes, according to Tina Reiswig, one of Buer's employees. Her remains, which washed onto a San Francisco Bay shore in April 2003, wore khaki pants.

Those and other details emerged the day after Peterson's defense attorney made a bold claim that Laci Peterson's son was born alive -- and, therefore, Scott Peterson could not have been the killer.

Mark Geragos' (search) surprising promise, which one legal observer called "dramatic, but dangerous," highlighted the defense's opening statement Wednesday.

After Geragos spent two hours picking apart the prosecution's case, the first in that line of witnesses, the couple's housekeeper, briefly took the stand Wednesday.

Margarita Nava discussed how she cleaned the couple's kitchen floor the day before Laci Peterson was reported missing. Prosecutors believe Scott Peterson cleaned and mopped his kitchen after killing his wife, and have seized the mop as evidence.

Before Nava testified, Geragos told jurors that prosecutors have nothing more than flimsy circumstance against his client.

He will call experts to testify that the fetus was older than it would have been if it died on Dec. 24 -- the day Peterson says he last saw his wife alive before going fishing on San Francisco Bay. Prosecutors have said their experts will testify that the fetus was expelled well after Laci Peterson's corpse was dumped into the bay.

It was the first formal glimpse at a strategy to clear Peterson by suggesting that somebody else was the killer.

Geragos' gamble took some legal observers by surprise. Robert Talbot, a professor at the University of San Francisco School of Law, called move "dramatic, but dangerous."

"But if he can do it, it will go a long way to reasonable doubt," he said.

Prosecutors have portrayed Peterson as a lying cheat who killed his wife because he was having an affair with massage therapist Amber Frey -- and because he wasn't ready to become a father.

Geragos countered Wednesday that the former fertilizer salesman was "boorish" and a "cad" who did have a mistress -- but while that may not be defensible, it doesn't mean he killed his wife.

Geragos downplayed Peterson's interest in Frey, saying they only went out on two dates, and characterized him as a giddily expectant father who accompanied his wife to all her doctor's appointments.

"He's not charged with having an affair," Geragos said. "The fact of the matter is that this is a murder case and there has to be evidence in a murder case."

During his own opening statements Tuesday, prosecutor Rick Distaso didn't promise jurors they would hear about a murder weapon or an eyewitness to the crime.

Geragos later raised another alternative to the prosecution's theory by pointing to witnesses who reported seeing a suspicious van in the neighborhood around the morning Laci Peterson disappeared. He said another saw her being shoved into a van days after Dec. 24.

Instead of investigating other leads, authorities in the couple's hometown of Modesto "turned his life upside down" as they single-mindedly pursued Peterson, Geragos said. They even ignored their own best intelligence, Geragos suggested, when they focused on Peterson even though a Modesto detective had told a judge that "Scott Peterson couldn't have acted alone."