Scott Peterson's (search) defense lawyer promised jurors during opening statements three months ago that testimony would show police found "zip, nada, nothing" in their investigation that would implicate Peterson in the killing of his pregnant wife.

On Tuesday, Mark Geragos (search) hammered that point in his cross-examination of a witness who testified she found no blood on any of the tattered clothing on the remains of Laci Peterson that washed up on the shore of San Francisco Bay (search) months after she disappeared.

Pin Kyo, a state Department of Justice criminalist, said she did find a few specks of blood on a comforter cover from the Petersons' bedroom, but another witness from the same agency -- criminalist William Hudlow -- later testified that DNA testing indicated the blood came from Scott Peterson.

Prosecutors have not said how they believe Peterson killed his pregnant wife, and the body was too decomposed to determine a cause of death.

Prosecutors are trying to prove Peterson killed his wife on or around Dec. 24, 2002, then dumped her weighted body into the bay. The bodies of Laci and her fetus washed up along the bay in April 2003 not far from where Scott Peterson says he launched his boat that Christmas Eve for a solo fishing trip.

Earlier Tuesday, Kyo gave testimony that cast doubt on defense theories of the case. She said duct tape found on Laci's remains did not match duct tape discovered near where her body washed ashore, and that no tissue or blood was found on a large tarp-like piece of plastic found nearby.

Defense lawyers have implied the plastic and the duct tape may have had some connection to Laci's body.

Kyo said she also tested twine-like material taken from around the fetus' neck.

Defense lawyers have claimed Laci was abducted, and that the child was born alive and then murdered. They have hinted that they believe the twine was intentionally tied around its neck.

Showing a picture of the twine to jurors, prosecutor Dave Harris asked Kyo about what appeared to be a small loop tied off with a knot.

"The way it's tied is very loosely," Kyo said.

On cross-examination, though, Kyo acknowledged that one knot did appear to be tightly tied.

Geragos then walked Kyo through each item she was asked to test for blood, getting her to say repeatedly that nothing was found. He led her back to testimony from Monday when she told jurors she found no blood on two mops and a bucket seized from the Petersons' home. Prosecutors have implied Peterson used the mops to clean the murder scene, but have presented no evidence to support that theory.

"There was absolutely nothing on it, right?" Geragos asked.

"That is correct," Kyo replied.

She acknowledged that no blood was found on a small folding knife, nothing in a toolbox in Peterson's pickup truck in which police allege he stored his dead wife's body, no blood on two pairs of shoes, on Peterson's boat cover or on numerous articles of clothing.

"All negative for blood, right?" Geragos prodded.

"That is correct," Kyo said.

Geragos also suggested that Kyo exaggerated when she testified that she'd found chunks of concrete in Peterson's boat.

"Now this is what was called the chunks of concrete, is that correct?" Geragos asked, holding out in his hand the tiny pieces flecked on paper.

"That is correct," Kyo said.

In a display of courtroom theatrics, Geragos then pulled out a small bucket-sized cement anchor Peterson claims he made for his boat.

"Now, that's a chunk of concrete," Geragos said. Geragos walked slowly in front of jurors with the anchor and the concrete pieces, holding both out for their examination.

Prosecutors claim Peterson used the rest of an 80-pound bag of concrete to make other anchors he used to weight his wife's body in the bay, but Geragos has said Peterson used the extra material to fix his driveway.

There has been no testimony yet about whether concrete samples taken from Peterson's driveway matched the concrete used to make the anchor.

Some legal observers speculated that Geragos may be moving toward not putting on any defense case at all. The prosecution is expected to rest by the end of the month.

"They haven't put enough evidence on to mandate that the defense put on a case," said former prosecutor Michael Cardoza, who is observing the trial. "Right now, it would be tempting for me not to put on a defense case at all. But it's going to take the courage of a lion to do that."

Former prosecutor Chuck Smith, also observing the trial, agreed that the defense may likely rest its case before it even begins.

"I think it's very likely," Smith said. "Almost every theory the prosecution tries to prove, Geragos has defeated."