Ramirez was born in El Paso, Texas, on February 29, 1960, the youngest of Julian and Mercedes Ramirez's five children. His father, a Mexican national and former Juarez policeman who later became a laborer on the Santa Fe railroad, was a hard-working man prone to fits of anger that often resulted in physical abuse.

Ramirez, or "Richie", as he was known to his family, was present on May 4, 1973, when his cousin Mike fatally shot his wife, Jessie, in the face with a .38 caliber revolver during a domestic argument. After the shooting Richie became sullen and withdrawn from his family and peers. Later that year, he moved in with his older sister, Ruth, and her husband, Roberto, an obsessive "peeping Tom" who took Richie along on his nocturnal exploits. Ramirez also began using LSD and cultivated an interest in Satanism.

Mike was found not guilty of Jessie's murder by reason of insanity (with his combat record as a mitigating factor) and was released in 1977, after four years of incarceration at the Texas State Mental Hospital. His influence over Richard continued.

Erickson was able to give a detailed description of the assailant to investigators, and police were able to obtain a cast of Ramirez's footprint from the Romero house. The stolen car was found on August 28 in Wilshire Center, Los Angeles, and police were able to obtain a single fingerprint from the rear view mirror despite Ramirez's careful efforts to wipe the car clean of his prints. The print was positively identified as belonging to Richard Muñoz Ramirez, who was described as a 25-year-old drifter from Texas, with a long rap sheet that included many arrests for traffic and illegal drug violations. Law enforcement officials decided to release to the media a mug shot of Ramirez from a December 12, 1984 arrest (photo, below right) for car theft, and "The Night Stalker" finally had a face. At the police press conference it was announced: "We know who you are now, and soon everyone else will. There will be no place you can hide."

On August 30, 1985, Ramirez took a bus to Tucson, Arizona, to visit his brother, unaware that he had become the lead story in virtually every major newspaper and television news program across the state of California. After failing to meet his brother, he returned to Los Angeles early on the morning of August 31. He walked past officers, who were staking out the bus terminal in hopes of catching the killer should he attempt to flee on an outbound bus, to a convenience store in East Los Angeles. After noticing a group of elderly Mexican women fearfully identifying him as "El Matador" (or "The Killer"), Ramirez saw his face on the covers on the newspaper rack and fled the store in a panic. After running across the Santa Ana Freeway, he attempted to carjack a woman but was chased away by bystanders, who pursued him. After hopping over several fences and attempting two more carjackings, he was eventually subdued by a group of residents, one of whom had struck him over the head with a metal bar in the pursuit. The group held him down, relentlessly beating him until police arrived and took Ramirez into custody.

Jury selection for the case started on July 22, 1988. At his first court appearance, Ramirez raised a hand with a pentagram drawn on it and yelled "Hail Satan". On August 3, 1988, the Los Angeles Times reported that some jail employees overheard Ramirez planning to shoot the prosecutor with a gun, which Ramirez intended to have smuggled into the courtroom. Consequently, a metal detector was installed outside the courtroom, and intensive searches were conducted on people entering. On August 14, the trial was interrupted because one of the jurors, Phyllis Singletary, did not arrive at the courtroom. Later that day, she was found shot to death in her apartment. The jury was terrified; they could not help wondering if Ramirez had somehow directed this event from inside his prison cell, and if he could reach other jury members. However, Ramirez was not responsible for Singletary's death; she had been shot and killed by her boyfriend, who later committed suicide with the same weapon in a hotel. The alternate juror who replaced Singletary was too frightened to return to her home.

On September 20, 1989, Ramirez was convicted of all charges: 13 counts of murder, 5 attempted murders, 11 sexual assaults, and 14 burglaries. During the penalty phase of the trial, on November 7, 1989, he was sentenced to die in California's gas chamber. He stated to reporters after the death sentences, "Big deal. Death always went with the territory. See you in Disneyland."

By the time of the trial, Ramirez had fans who were writing him letters and paying him visits. Beginning in 1985, Doreen Lioy wrote him nearly 75 letters during his incarceration. In 1988, he proposed to her, and on October 3, 1996, they were married in California's San Quentin State Prison. For many years before Ramirez's death, Lioy stated that she would commit suicide when Ramirez was executed. However, Lioy and Ramirez eventually separated. By some estimates, he would have been in his early seventies before his execution was carried out, due to the lengthy California appeals process.

On August 7, 2006, his first round of state appeals ended unsuccessfully when the California Supreme Court upheld his convictions and death sentence. On September 7, 2006, the California Supreme Court denied his request for a rehearing. Ramirez had appeals pending until the time of his death.

When it was discovered that the ballistic and shoe print evidence from the Night Stalker crime scenes matched the Pan crime scene, then-mayor of San Francisco Dianne Feinstein divulged the information in a televised press conference. This leak infuriated the detectives in the case, as they knew the killer would be following media coverage giving him opportunity to destroy crucial forensic evidence. Ramirez, who had indeed been watching the press, dropped his size 11 1/2 Avia sneakers over the side of the Golden Gate Bridge that night. He remained in the area for a few more days before heading back to the Los Angeles area.

Ramirez died of complications secondary to B-cell lymphoma, at Marin General Hospital in Greenbrae, California, on June 7, 2013. He had also been affected by "chronic substance abuse and chronic hepatitis C viral infection". At 53 years old, he had been on death row for more than 23 years.

The trial cost $1.8 million, ($3.55 million in 2017 dollars) which at the time made it the most expensive in the history of California, until surpassed by the O. J. Simpson murder case in 1994.