Scott Lee Peterson was born October 24, 1972, at Sharp Coronado Hospital in San Diego, California, to Lee Arthur Peterson, a businessman who owned a crate-packaging Business, and Jacqueline "Jackie" Helen Latham, who owned a boutique in La Jolla called The Put On. Though Lee and Jackie had six children from previous relationships, Scott was their only child together. As a child, he shared a bedroom with his half-brother John (Jackie's son from a previous relationship) in the family's two-bedroom apartment in La Jolla.

Peterson began playing golf at an early age, a result of time he spent on them with his father. By age 14, he could beat his father at the game. For a time, he had dreams of becoming a professional Golfer like Phil Mickelson, his teammate at the University of San Diego High School. By the end of high school, he was one of the top junior golfers in San Diego. In 1990, Peterson enrolled at Arizona State University (where Mickelson had also enrolled) on a partial golf scholarship. Mickelson would go on to become a highly successful PGA Golfer, with Lee Peterson later testifying that his son was discouraged by the considerable competition that Mickelson presented at Arizona State. Randall Mell of the Fort Lauderdale, Florida Sun-Sentinel reported that Chip Couch, the father of Arizona State Golfer Chris Couch, had told Mell that he got Peterson kicked off the golf team after giving Chris a hangover after a night of partying. As Chris was the No. 1 junior in the country, Chip did not want Peterson to threaten his son's Future, and complained to the golf coach, who kicked Peterson off the team. Peterson transferred to Cuesta College in San Luis Obispo, California, and later, California Polytechnic State University. He initially planned to major in international Business, but changed his major to agricultural Business. Professors who taught Peterson describe him as a model student. His agribusiness professor Jim Ahern commented, "I wouldn't mind having a class full of Scott Petersons."

While at Cal Poly, Peterson worked at a restaurant in Morro Bay called the Pacific Café. One of his co-workers would receive visits from a neighbor of his named Laci Denise Rocha, who also attended Cal Poly as an ornamental horticulture major. When Peterson and his Future wife first met at the restaurant in mid-1994, Laci made the first move, sending him her phone number. Immediately after meeting him, Laci told her mother that she had met the man that she would marry. Peterson later called Laci, and they began dating, their first date being a deep-sea fishing trip on which Laci got seasick. As Peterson's relationship with Laci grew more serious, he put aside his dreams of professional golf in order to focus on a Business path. The couple dated for two years and eventually moved in together. In 1997, after Laci graduated, they married at Sycamore Mineral Springs Resort in San Luis Obispo County's Avila Valley. While Peterson finished his senior year, Laci took a job in nearby Prunedale. Prosecutors have stated that around this time, Peterson engaged in the first of at least two extramarital affairs, though they have not revealed a name or details of this relationship.

Peterson graduated with a BS in agricultural Business in June 1998. After their graduations, Peterson and Laci opened a Sports bar in San Luis Obispo called The Shack. Contrary to a Los Angeles Times story that reported that Peterson's parents loaned him money to open the establishment, Peterson's parents emphatically told the San Francisco Chronicle that they did not, believing it was a bad investment. When the couple had difficulty finding a technician to install a needed vent in the restaurant, Peterson took the necessary certification course in Los Angeles in order to install it himself. Business was initially slow, but eventually picked up, especially on weekends. The Petersons sold The Shack in 2000 when they moved to Laci's hometown of Modesto to start a family. In October 2000, they purchased a three-bedroom, two-bath bungalow house for $177,000 on Covena Avenue in an upscale neighborhood near La Loma Park.

Dr. Charles March was expected to be a crucial witness for the defense, one who, according to the San Francisco Chronicle, could single-handedly exonerate Peterson by showing that Laci's fetus died a week after prosecutors claimed. Under cross-examination, March admitted basing his findings on an anecdote from one of Laci's friends that she had taken a home pregnancy test on June 9, 2002. When prosecutors pointed out that no medical records relied on the June 9 date, March became flustered and confused on the stand and asked a prosecutor to cut him "some slack", undermining his credibility. Summing up this key defense witness, Stan Goldman, a Criminal law professor at Loyola Law School in Los Angeles said, "There were moments today that reminded me of Chernobyl." According to one newspaper account about March's testimony, "by the end of his testimony Thursday, legal analysts and jurors closed their notebooks, rolled their eyes, and snickered when they thought no one was looking".

On April 21, 2003, Peterson was arraigned in Stanislaus County Superior Court before Judge Nancy Ashley. He was charged with two felony counts of murder with premeditation and special circumstances: the first degree murder of Laci, and the second degree murder of Connor. He pled not guilty.

On November 12, 2004, a jury convicted Peterson of two counts of murder: first-degree murder with special circumstances for killing Laci, and second-degree murder for killing the fetus she carried. The penalty phase of the trial began on November 30, and concluded December 13, when the jury recommended that Peterson be sentenced to death. On March 16, Judge Alfred A. Delucchi followed the recommendation of the jury, sentencing Peterson to death by lethal injection and ordering him to pay $10,000 toward the cost of Laci's funeral, calling the murder of Laci "cruel, uncaring, heartless, and callous".

Peterson arrived at San Quentin State Prison in the early morning hours of Wednesday, March 17, 2005. He was reported not to have slept the night before, being too "jazzed" to sleep. He joined the more than 700 other inmates in California's sole death row facility while his case is on automatic appeal to the Supreme Court of California in San Francisco.

Cliff Gardner, Peterson's attorney, stated that the publicity surrounding the trial, incorrect evidentiary rulings, and other mistakes deprived Peterson of a fair trial. On July 6, 2012, Gardner filed a 423-page appeal of Peterson's sentence. The State Attorney General's office filed their response brief on January 26, 2015. The defense filed a response to the State's brief in July 2015, claiming that a certified dog that detected Laci's scent at Berkeley Marina had failed two-thirds of tests with similar conditions.

In later press appearances, members of the jury stated that they felt that Peterson's demeanor—specifically his lack of emotion and the phone calls to Frey in the days following Laci's disappearance—indicated that he was guilty. They based their verdict on "hundreds of small 'puzzle pieces' of circumstantial evidence that were revealed during the trial, from the location of Laci's body to the myriad of lies her husband told after her disappearance". The jury decided on the death penalty because they felt that Peterson betrayed his responsibility to protect his wife and son.

In November 2015, the defense filed a habeas corpus petition, claiming that a juror lied on her jury application, and that there was evidence that neighbors saw Laci alive after Scott left home. On August 10, 2017, the State Attorney General responded to the appeal by filing a 150-page document contesting the notion disputing the claims put forward in the appeal, stating that the appeal ignored "overwhelming evidence" that Peterson murdered Laci. Supervising Deputy Attorney General Donna Provenzano stated that the timeline of the crime was established by the neighbor who found the Petersons' golden retriever wandering in the street with its leash still attached, before the sightings of Laci and her dog. Provenzano also indicated, "Purported sightings of Laci were legion," noting 74 reported sightings in 26 states and overseas, most of which she stated, were neither viable nor corroborated.