Jurors cringed Wednesday as prosecutors displayed photos of bone and tissue taken from the decomposed bodies of Scott Peterson's (search) dead wife and their fetus.

In graphic testimony Wednesday morning, two sheriff's deputies testified at Peterson's double-murder trial about the condition of the remains and where they were discovered.

Deputy Chris Martinez of the Contra Costa County Sheriff's Department said the fetus was so decayed that he had to roll the remains onto a towel to move them.

Defense attorney Mark Geragos (search) questioned what evidence authorities collected when they retrieved those remains, which were found in a marshy shore of San Francisco Bay (search).

"Fair to say that there was nobody going around collecting evidence?" Geragos asked.

"When I was there, no," Martinez responded.

Prosecutors have abruptly changed the direction of their case against Peterson after questioning witnesses about his affair -- the alleged motive for murder -- last week.

The move seemed to highlight a shift in the prosecution's strategy to focus more on the murder than on Peterson's seemingly odd behavior in the days before and after his pregnant wife vanished.

Testimony has turned to the discovery of Peterson's dead wife and the couple's fetus along the Bay shore.

Elena Gonzalez testified she found the body -- mostly just a torso -- half-submerged in the water along a rocky embankment. Gonzalez, who resumed her testimony Wednesday, said she saw a dog sniffing around Laci Peterson's remains.

On Tuesday, Michael Looby testified that he and his wife were walking their dog in Richmond along the bay on April 13, 2003, when he came upon a body in a marshy area.

"It was a body of a small baby," Looby said, adding that he and his wife walked to a nearby home and asked the residents to call 911.

The body of Peterson's wife, Laci, washed ashore a day later, not far from where the fetus was found.

Prosecutors say Peterson's affair drove him to kill his pregnant wife on or around Dec. 24, 2002. They say he then dumped her body in San Francisco Bay. Defense lawyers say someone else abducted her near their Modesto home as she walked her dog, held her captive before killing her and dumped her body to frame Peterson.

Geragos appeared to push his theory that the fetus was killed after birth with his questioning of Richmond police officer Tod Opdyke, one of the first to respond to the scene.

"Did you notice ... what appeared to be some tape or twine around the baby's neck?" Geragos asked, using hand gestures to motion in a manner as if he was tying something around his own neck.

Opdyke called it "tapelike substance."

Geragos has previously charged that the fetus had something physically tied around its neck. Prosecutors say it was simply debris from the water.

Geragos then asked Richmond police officer Timothy Gard if he found anything in the area that resembled the tape or twine wrapped around the fetus' neck.

Gard testified he searched the area for evidence.

"Anywhere along that entire ... shore did you see any plastic twine or anything that looked consistent with the item you saw tied around the baby?" Geragos asked.

"No," Gard replied.

Prosecutors then objected to the use of the word "tied." Judge Alfred A. Delucchi said he would leave it up to jurors to determine whether the material was tied around the fetus' neck or simply wrapped.

Meanwhile, jurors seemed visibly bothered as lawyers displayed pictures of the badly decomposed bodies. Some rubbed their foreheads or covered their mouths. Peterson did not look at the large screen where the pictures were displayed and Laci's parents, who have been present throughout the trial, left the courtroom.

Earlier in the day, California Department of Justice polygraph expert Douglas Mansfield testified that he interviewed Peterson on Dec. 25, 2002, a day after Laci vanished.

Mansfield said Peterson told him neither he nor Laci were having an affair.

Peterson said his marriage to Laci was fine.

"He said there was no third parties .... involved with him or his wife," Mansfield said.

On cross-examination, Mansfield described Peterson as "very cooperative" during the interview that lasted about two hours and 45 minutes.

Mansfield was not identified to the jury as a polygraph examiner -- he was described only as an employee of the state Justice Department -- and the context of his questioning of Peterson that day was not made clear in court. Polygraph examinations are generally not admissible as evidence.