A reporter who gained access to the nation's largest death row in California inadvertently discovered that she had captured pictures of Scott Peterson, who was convicted of murder more than seven years ago.

In a highly-publicized case, Peterson was sentenced to death in 2005 for the murder of his wife, Laci Peterson, and their unborn child in California. He is currently on death row at the San Quentin State Prison in California.

Nancy Mullane, an independent reporter and producer, told TODAY's Matt Lauer on Wednesday that she has been going inside the facility as a reporter since 2007.

"There have been no reporters on death row in California in almost a decade," Mullane said. "So it took me years to build a relationship with the California Department of Corrections where they actually trusted me to be the first reporter to go in."

While spending time inside death row doing interviews with prisoners serving life in the San Quentin facility, she was allowed to take photos as part of her reporting.

"It wasn't until two months later that I was actually reviewing the photographs and I realized, 'Oh, I think these are Scott Peterson,'" Mullane said.

She described Peterson's environment in death row as "confined" and said that 68 prisoners live in his section of the facility. He reportedly has his own cell and can spend a few hours per day outside exercising or playing basketball.

Mullane did not get a chance to speak with Peterson, but did get to interview inmates willing to talk from their cell doors. Her reporting and observations are documented in a new book, "Life After Murder: Five Men in Search of Redemption."

 Related: Can a convicted murderer find redemption after the verdict?

In the last five years, Mullane has been studying and reporting on prisoners who are serving life in prison with the possibility of parole.

"What I have found is this is a population we don't know in prisons," Mullane said. "We don't know what people who commit a murder really are like after they've done the time, after they've done everything we've asked them to do."

Peterson is not part of that population, having been sentenced to death. He still claims innocence, and in July filed an appeal of his murder conviction with the California Supreme Court. The appeal is expected to take years to resolve.

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