For much of an hour, FBI lab supervisor Constance L. Fisher explained the mitochondrial DNA analysis used to compare Laci Peterson's hair with one strand in the boat Peterson said he used to go fishing the day his wife disappeared on Christmas Eve.
The families of both Scott and Laci Peterson were in the courtroom for the preliminary hearing.
Peterson is charged with murder in the deaths of his wife and their unborn son and could get the death penalty.
Peterson reported his 27-year-old wife missing when he returned home from a solo Christmas Eve fishing trip. She was eight months pregnant with a boy they planned to name Conner.
The remains of mother and son were found four months later in April, along the San Francisco Bay, within miles of where Peterson said he had been fishing.
Peterson's lawyer, Mark Geragos, disputed the admissibility of the DNA evidence and also suggested someone may have tampered with the hair found on the boat. It was originally listed as a single hair, but prosecutors said it broke in half during their investigation.
The hearing is expected to give the most detailed picture to date about what clues led investigators to suspect Scott Peterson from the beginning.
The 31-year-old former fertilizer salesman has been held without bail since he was arrested not far from the Mexico border with his hair bleached and $10,000 in cash. In the months after Laci Peterson's disappearance, it was disclosed that her husband was having an affair.
Geragos has said he would not only prove Peterson innocent, but would find the "real killers." The defense team has intimated that a satanic cult may have been responsible.
CBS Legal Analyst Andrew Cohen notes it's clear from Day One that this is going to be a pitched battle all the way through the preliminary hearing.
"Prosecutors need to put on a strong presentation in order to ensure that Peterson stays in jail pending trial and defense attorneys have to challenge everything all the way because this is a capital case and Peterson's life is on the line.
"You can tell by the battle over this hair how important it will be to the case. If prosecutors can get it into evidence at trial, it will help them link Laci Peterson to Scott Peterson's boat and that would be a major part of the murder case. The defense on the other hand either has to try to keep it out of evidence or challenge its reliability,'' says Cohen.