Lyle and Erik Menendez

As in their pretrial detention, the California Department of Corrections separated the brothers and sent them to different prisons. Since they were considered to be maximum-security inmates, they were segregated from other prisoners. They remained in separate prisons until February 2018, when Lyle was moved from Mule Creek State Prison in northern California to the Richard J. Donovan Correctional Facility in San Diego County; where they were housed in separate units. Erik also spent some time at Pleasant Valley Prison in Coalinga, California.

On April 4, 2018, Lyle was moved into the same housing unit as Erik, reuniting them for the first time since they began serving their sentences nearly 22 years earlier. The brothers burst into tears and hugged each other at their first meeting in the housing unit. The unit where they are housed is reserved for inmates who agree to participate in education and rehabilitation programs without creating disruptions.

In 2010, A&E released Mrs. Menéndez, a documentary about Tammi. In late 2017, A&E aired a five-part documentary titled The Menendez Murders: Erik Tells All, in which Erik describes via telephone the murders and the aftermath. The series also shows never-before-seen photos and new interviews with prosecutors, law enforcement, close family and friends, and medical experts.

In 2005, Tammi self-published a book, They Said We'd Never Make It – My Life with Erik Menéndez, but she said on CNN's Larry King Live that Erik also "did a lot of editing on the book." In an interview with People magazine, she stated:

On June 12, 1999, Erik married Tammi Ruth Saccoman at Folsom State Prison in a prison waiting room. Tammi later stated: "Our wedding cake was a Twinkie. We improvised. It was a wonderful ceremony until I had to leave. That was a very lonely night." In an October 2005 interview with ABC News, she described her relationship with Erik as "something that I've dreamed about for a long time. And it's just something very special that I never thought that I would ever have."

On February 27, 1998, the California Court of Appeal upheld the brothers' murder convictions, and on May 28, 1998, the Supreme Court of California declined to review the case, thus allowing the decision of the appellate court to stand. Both brothers filed habeas corpus petitions with the Supreme Court of California, which were denied in 1999. Having exhausted their appeal remedies in state court, they filed separate habeas corpus petitions in the United States District Court. On March 4, 2003, a magistrate judge recommended the denial of the petitions, and the district court adopted the recommendation. They then decided to appeal to the United States Court of Appeals for the Ninth Circuit. On September 7, 2005, a three-judge panel denied both their habeas corpus petitions, although Judge Alex Kozinski stated that the trial judge changed many of his rulings during the two trials.

During the penalty phase of the trial, Abramson (the brothers' defense lawyer), apparently told a defense witness named William Vicary to edit his own notes, but the district attorney's office decided not to launch a criminal investigation on Abramson. Both brothers also filed motions for a mistrial, claiming that they suffered irreversible damage in the penalty phase as a result of possible misconduct and ineffective representation by Abramson. On July 2, 1996, Weisberg sentenced the brothers to life in prison without the possibility of parole, and also sentenced them to consecutive sentences for the killings and the charges of conspiracy to commit murder.

On July 2, 1996, Lyle married Anna Eriksson at a ceremony attended by Abramson and his aunt Marta Menéndez, and presided over by Judge Nancy Brown; they divorced on April 1, 2001 after Eriksson discovered that Lyle was allegedly cheating on her with another woman. In November 2003, Lyle married Rebecca Sneed at a ceremony in a visiting area of Mule Creek State Prison; they had known each other for around ten years before their engagement.

The Menéndez case became a national sensation when Court TV broadcast the trial in 1993. Represented by their defense lawyer, Leslie Abramson, the brothers stated that they killed their parents out of fear for their lives after a lifetime of abuse at the hands of their parents, especially sexual abuse at the hands of their father, who was described as a cruel perfectionist and pedophile. Meanwhile, their mother was described as an enabling, selfish, mentally unstable alcoholic and drug addict who encouraged her husband's behavior and was also violent towards the brothers.

During the early stages of the investigation, police tried to narrow their search to suspects who had motives to kill José and Kitty. They also investigated potential mob leads. As their investigation continued, police began to suspect that the brothers were the most likely perpetrators because of the obvious financial motive and their exorbitant spending after the killings. In an attempt to get a confession from Erik, police arranged for his friend Craig Cignarelli to wear a wire during a lunch with Erik at a local beachfront restaurant, but when Cignarelli asked Erik whether he had killed his parents, Erik denied it. Erik eventually confessed to his psychologist Jerome Oziel, who then told his mistress, Judalon Smyth. Smyth later broke up with Oziel and told the police about the brothers' involvement. Lyle was arrested on March 8, 1990, and Erik turned himself in three days later after returning to Los Angeles from Israel. Both were held without bail and kept separate from each other.

In August 1990, Judge James Albrecht ruled that tapes of the conversations between Erik and Oziel were admissible evidence since Oziel stated that Lyle allegedly threatened him and violated doctor–patient privilege. Albrecht's ruling was appealed, after which the proceedings were delayed for two years. The Supreme Court of California ruled in August 1992 that most of the tapes were admissible with the exception of the tape on which Erik was recorded discussing the murders. After that decision, a Los Angeles County grand jury issued indictments in December 1992, charging the brothers with the murders of their parents.

On the evening of August 20, 1989, José and Kitty were standing in the den of their Beverly Hills mansion when Lyle and Erik entered the den carrying shotguns. José was shot 6 times, including the fatal shot in the back of the head with a Mossberg 12-gauge shotgun. Kitty was shot 10 times in total. Before the fatal shot to her cheek, she was on the ground, slowly crawling and moaning. Lyle then ran to his car to reload, and then fired the fatal shot to her face.

Erik testified that a couple weeks before the night of the killings, that he told his brother about the sexual abuse he was experiencing, which then led to several confrontations within the family. They also testified that their father threatened to kill them if they did not keep the abuse a secret. They claimed that the last confrontation happened inside the house den on August 20, 1989, a few minutes before Kitty and José were killed. The brothers then stated that their father closed the den's door at that time, which was unusual. Paranoid and afraid that they would be killed by their own parents, Lyle and Erik went outside of the house to load their shotguns. Erik stated, "As I went into the room, I just started firing."

In 1986, José's career as a corporate executive (he had recently joined the company then known as International Video Entertainment) took the family to Beverly Hills, California. The following year, Erik began attending Beverly Hills High School, where he earned average grades and displayed a remarkable talent for tennis, ranking 44th in the US for 18-and-under players. Lyle attended Princeton University from which he later was suspended for plagiarism. Before Lyle was suspended, he was on academic and disciplinary probation for poor grades.

In the summer of 1976, Lyle and Erik's cousin Vander Molen, would often stay at the Menendez house in the summer. Lyle told her about how he was being sexually abused by his father and what he did to them. After that Vander Molen told Kitty Menendez and she did not believe what Lyle said. Kitty then took Lyle upstairs and that was the last Vander Molen heard anything about it.

Joseph Lyle Menendez (born January 10, 1968) and Erik Galen Menendez (born November 27, 1970) are American brothers who were convicted in 1996 for the murders of their parents, José and Mary Louise ("Kitty") Menéndez.

The couple's first son, Joseph Lyle Menéndez, who goes by his middle name, was born on January 10, 1968, in New York. Kitty quit her teaching job after Lyle was born, and the family moved to New Jersey, where Erik was born on November 27, 1970, in Gloucester Township. In New Jersey, the family lived in Hopewell Township and both brothers attended Princeton Day School.

Lyle and Erik's father, José Enrique Menéndez, was born on May 6, 1944, in Havana, Cuba. At age 16, shortly after the start of the Cuban Revolution, he moved to the United States. José attended Southern Illinois University, where he met Mary Louise "Kitty" Andersen (1941–1989). They married in 1963 and moved to New York City, where José earned an accounting degree from Queens College.