Scott Peterson's (search) attorney got a detective to acknowledge that police questioned hundreds of registered sex offenders (search) and parolees as possible suspects in the murder of Peterson's wife, but never found 24 and did not always check alibis.

One potential suspect even confessed to the crime but the man's admission was discounted because he had mental problems, Detective Ray Coyle said Monday under questioning from defense attorney Mark Geragos (search).

"He said he murdered a female named Lisa Peterson, right? ... He said the only witness was the dog ... He said he broke her neck?" Geragos asked Coyle.

"Yes," Coyle replied.

Coyle was originally called by the prosecution last week to testify about the extensive search for evidence at Peterson's home, but Geragos quickly asked questions about the sex offenders and parolees who lived near the Peterson's Modesto home.

The detective said Monday that after police tracked down 285 of the 309 sex offenders and parolees living in the area, they closed most of the files without ruling them out as suspects or confirming their whereabouts on Dec, 24, 2002, the night Laci Peterson was reported missing.

Coyle, who is set to return to the witness stand Tuesday, said he was still working to track down the remaining 24 offenders.

Holding a list of names in his hand, Geragos asked the detective about several sex offenders with sketchy alibis. One said he was out of state visiting his sister on that Christmas Eve, yet police were never able to substantiate his story, Coyle said.

"That was the extent of the investigation as far as you know?" Geragos asked.

"Yes," Coyle said.

Prosecutors allege Peterson murdered his pregnant wife on or around Dec. 24 , 2002, then drove to San Francisco Bay and dumped the body. Peterson acknowledges being on the bay that day, but said he went fishing alone and returned to an empty home. Geragos asserts that someone else abducted and killed Laci, then framed her husband.

Earlier Monday, Detective Henry "Dodge" Hendee testified under cross-examination that residue from seven suspicious stains collected from Peterson's pickup truck were not blood, and that no incriminating evidence was found in a large tool box in the bed of the vehicle.

Prosecutors allege Peterson used the tool box to conceal Laci's body during the drive from the couple's home to the bay.

Geragos peppered the detective with questions about tests on other stains found in the Peterson kitchen, bedroom and on a pair of gloves taken from Peterson's truck, repeatedly asking, "What were the results?"

"Negative," Hendee replied.