This much is not in dispute. William Richards' wife, Pamela, was strangled and her skull smashed in the summer of 1993. A California jury convicted Richards of the slaying after hearing now-recanted bite-mark testimony.
But California judges have disagreed about whether that change in testimony was grounds for tossing Richards' conviction. Now, almost two decades after Richards was sentenced to 25 years to life in prison, his attorneys are hopeful a new state law inspired by his case will set him free.
The law, which took effect in January, makes it easier for a defendant to get a conviction overturned when experts recant their testimony. It prompted attorneys for the 65-year-old Richards, who has always maintained his innocence, to again ask the California Supreme Court to throw out a jury's guilty verdict.
Legal experts say the law will impact a wide variety of cases where experts later have second thoughts about their testimony. And it gives attorneys fighting to exonerate their clients an important new tool.
"More and more, experts are reconsidering their opinion not because they have pangs of guilt, but because in fact the science changes," said Laurie Levenson, a criminal law professor at Loyola Law School. "You want a legal system that recognizes that reality."
A San Bernardino County jury convicted Richards in 1997 of first-degree murder following expert testimony that a mark on his wife's hand was consistent with a unique feature of Richards' teeth. That expert, a forensic dentist, later recanted, saying he was no longer sure the injury was even a bite mark.
A San Bernardino County judge overturned Richards' conviction, but a state appeals court reinstated it. In a 4-3 decision in 2012, the State Supreme Court sided with the appeals court, saying a change in expert testimony does not necessarily make it false and thus possible grounds to vacate a conviction. The testimony must be shown to be "objectively untrue," the majority said.
The court also said doubts about the dentist's testimony and other new evidence raised by the defense did not clearly point to Richards' innocence when weighed against the "significant evidence pointing persuasively to ... guilt."
That evidence, according to prosecutors, was clear from the moment a sheriff's deputy responded to a 911 call from Richards just before midnight after he discovered his wife outside their mobile home. The deputy, Mark Nourse, said Richards knew a great deal about the crime scene though it was dark outside and Richards said he had no flashlight, according to court documents.
Prosecutors also presented a motive and physical evidence. Pamela Richards was openly having an affair and allegedly told a counselor a month before her slaying that she was afraid of her husband.
Blue fibers found in the crack of a broken fingernail on Pamela Richards' body were indistinguishable from those of the shirt Richards was wearing the night of the murder.
The San Bernardino County District Attorney's office declined comment about Richards' conviction, citing the ongoing case. But in a filing with the State Supreme Court in 2011, prosecutors said, "Motive and opportunity do not lie ... A jury sitting today would still find petitioner guilty beyond a reasonable doubt."
The defense has countered that the blue fibers were not present in a still photograph taken during the autopsy, suggesting they did not become lodged in her fingernail during the slaying. They also found that hair under one of Pamela Richards' fingernails and DNA on a paving stone that prosecutors said was used in the attack didn't come from Richards.
"The prosecution case was entirely circumstantial," said Richards' attorney, Jan Stiglitz, with the California Innocence Project at the California Western School of Law.
But the focus of the defense's appeals has been on the testimony by Norman Sperber about the mark on Pamela Richards' hand. Sperber was a well-known forensic dentist with a private practice in San Diego and had been called to testify at the trial of serial killer Ted Bundy, who was convicted with the help of bite-mark analysis.
At Richards' 1997 trial, he testified that only as many as two out of a 100 people would have Richards' unusual tooth feature. But later, with the help of a clearer photograph of the mark, he said Richards' teeth were not consistent with the mark on his wife's hand.
Reached by phone, Sperber, now 86, said he did not recall the details of Richards' case, but he had always strived to be objective regardless of whether he was called by the prosecution or defense.
"We're not trying to convict somebody, we're trying to get to the truth," he said.
Bite-mark testimony has been slammed by some defense attorneys as sham science, but Sperber said it still holds value as long as it's done by knowledgeable people.
The majority in the 2012 State Supreme Court ruling said Sperber's original testimony was not false because other experts still did not definitively rule Richards' teeth out as the source of the mark.
Leno said that decision was wrong, and his legislation responds to it. Expert testimony should be treated no differently from eyewitness testimony: when it's recanted, that's strong grounds for the conviction to be overturned, he said. His bill says any opinion that an expert repudiates is false evidence. Under state law, if the false evidence is shown to be key to the person's alleged guilt, the court has authority to overturn the conviction.
The governor signed the bill into law in September, and experts say it will likely prompt the California Supreme Court to reconsider Richards' case.
The court is not under any deadline to make that decision, but Stiglitz said he is hopeful he will hear back by the middle of March.
"He's spent half his adult life in prison," Stiglitz said. "Every day counts."