Karen Korsberg, an FBI trace evidence expert, testified the hairs were consistent with hairs collected from a brush that belonged to Laci Peterson. She said her tests excluded the possibility that the hairs came from Scott Peterson.
On cross-examination, Korsberg acknowledged that she was unaware of a pubic hair collected from duct tape found on Laci's remains and never compared that to the samples she was given from Laci's hairbrush.
Korsberg said she forwarded the two hairs to another FBI lab for further testing, a technique known as mitochondrial DNA that can be used to determine a link between a hair, for example, and a person.
Such a technique is used when the hair does not have a root and brings with it a much lower degree of certainty than the so-called genetic fingerprinting that is widely used in courts.
The evidence is key to the prosecution's case that Laci Peterson was on the boat police allege Peterson kept secret from her and later used to dispose of her body.
Defense lawyers have attacked the mitochondrial testing, calling it the unreliable subject of "raging debate" among scientists. Experts estimate that half the states allow the technique as courtroom evidence, including California.
Defense lawyers have also previously attacked the way police collected the hairs from the pliers. Detectives testified that they took one hair from the pliers, but months later discovered two strands inside the evidence envelope.
Prosecutors on Tuesday sought to counter defense claims that police were so eager to charge their client with his wife's killing that they ignored other credible tips.
Two investigators testified that in the weeks after Laci Peterson vanished they pursued a tip that the pregnant schoolteacher was being held in a rural area about 30 miles from her hometown.
The testimony was intended to bolster the prosecution's contention that police exhausted all leads in their investigation of Laci's disappearance.
Modesto police officer Eric Beffa testified about an anonymous tip police received in early January 2003, just weeks after the disappearance, that Laci was being held captive near Tracy, a suburb west of Modesto.
On cross-examination, defense lawyer Mark Geragos noted the tip also included mention of a van.
Neighbors of the Petersons told police they saw a "suspicious" van with three men in the area around the time Laci vanished. It's a detail Geragos has continually brought up as he works to create reasonable doubt.
Beffa said he met with a San Joaquin County sheriff's deputy but was unable to find the location provided by the tipster.
That deputy, Paul Mears, testified that he continued to pursue the tip after the officer returned to Modesto.
Mears described a four-day search that ended with the discovery of a compound he said was "a bunch of shanties and shacks, old trailers that had been abandoned." Police found marijuana plants being cultivated but no connection to the Peterson case, he said.
Prosecutors allege Peterson killed his wife in their Modesto home on or around Dec. 24, 2002, then drove to San Francisco Bay and dumped her body. The badly decomposed remains of Laci Peterson and the couple's fetus washed ashore in April 2003, not far from where Peterson set out for what he claims was a solo fishing trip on the bay that Christmas Eve morning.
Defense lawyers contend someone else abducted and killed Laci, then framed their client after learning of his widely publicized alibi.
The trial entered its 15th week Tuesday.
In a day of wide-ranging testimony, prosecutors also called a real estate agent who testified Peterson approached her about selling the couple's home and a used car salesman who said Peterson traded in Laci's Land Rover for a Dodge pickup truck, all within weeks of her disappearance.
Sarah Yoshida, a criminalist with the state Department of Justice, testified Tuesday that she found no signs of blood or tissue on two pairs of Peterson's pliers seized by police, one of which was the tool where the hair was discovered.
Under cross-examination, Yoshida also acknowledged that swabs taken from both tools were never forensically tested. Yoshida said the pliers were rusty and showed no signs of recent use.
At day's end, Judge Alfred A. Delucchi told jurors the prosecution intends to wrap up its case by the end of September. The defense case is expected to take up to three weeks.
Outside court, Peterson's parents and Laci's parents appeared to have the first verbal confrontation of the trial.
Laci's stepfather, Ron Grantski, has spoken out previously about how ridiculous it is that Peterson went fishing on Christmas Eve, when Grantski himself would later testify that he, too, went fishing alone that morning.
"Where did you go fishing?" Peterson's father, Lee, said to Grantski on Tuesday as the families left the courtroom.
"You come down here and I'll tell you where I went fishing," Grantski replied sternly, heading down the courthouse escalator.