Richard Allen Davis was born on June 2, 1954, in San Francisco, California. He was the third of five children in his family. His parents were Robert Davis and Evelyn Smith. He had two older brothers named Donald and Ronald, and two younger sisters named Darlene and Patricia, the latter of whom passed away when she was young. Richard had partial Northern Paiute heritage through his maternal grandmother, Norma Wasson Johnny. For a time, Richard and his family lived with her before they moved to a house in La Honda, California.

Davis's early life was difficult. Both of his parents were alcoholics, and their behavior was often violent. His mother once punished him and his brothers for smoking by burning their hands on a hot stove. Richard experienced many violent fights between his parents. When he was nine years old, his parents separated. After the separation, his mother took Richard and his siblings back to live with their grandmother. When he was 11, the couple divorced. The children were allowed to choose whom to live with. Richard and his sisters chose to stay with their father, while his brothers chose their mother.

Richard's father, Robert, worked as a longshoreman but was often unable to take care of his children. He would send them to stay with different family members, caretakers, or women he was dating. Robert was also described as mentally unstable and abusive, often using physical punishment on Richard. He once broke Richard's jaw and pushed him through a wall. Robert married two more times, and Richard did not get along with either of his stepmothers.

At the age of 14, tragedy struck when his ten-year-old sister Patricia died from an illness. By this time, Richard was already getting into trouble with the law. He was placed on probation for burglary and forgery at 12 years old and was arrested again for burglary at 15. Davis dropped out of high school during his sophomore year. He later told a psychiatrist that stealing helped him relieve his stress.

At 17, he was in court for stealing a motorcycle. A judge offered him a choice between going to the California Youth Authority or joining the U.S. Army. Davis chose the Army and served for 13 months before receiving a general discharge.

In his later teenage years, Davis became involved in more criminal activities. He was arrested multiple times for burglary and served time in jail. He also received several diagnoses regarding his mental health, including avoidant personality disorder and antisocial personality disorder.

On October 1, 1993, Richard Allen Davis entered Polly Klaas's home in Petaluma, California, during a slumber party. Around 10:30 p.m., he threatened Polly and her friends with a knife taken from the kitchen. He tied up her friends, covered their heads with pillowcases, and directed them to count to 1,000. He then kidnapped Polly.

An all-points bulletin was broadcast shortly after the kidnapping. In the hours that followed, a babysitter noticed Davis's car, which was stuck in a ditch on a private driveway about 20 miles away. When the property owner passed by, she saw him and later reported it to the police. However, deputies who responded were unaware of the kidnapping and did not have enough information to detain Davis. He was allowed to leave after being asked to pour out an open beer container.

On November 28, 1993, the property owner found items that suggested a link to Polly's kidnapping while inspecting her land. This led investigators to identify Davis when they connected him to an earlier report filed by the deputies. A palm print found at the scene of the kidnapping was matched to Davis.

As authorities searched the area around Pythian Road, they monitored Davis, who was under surveillance. When initial searches did not yield results, police arrested him for kidnapping. On December 3, a massive search began for Polly Klaas, involving over 500 members from various agencies. The search focused on uncovering evidence but found no human remains initially.

On the evening of December 4, after hours of searching, Davis confessed to kidnapping and murdering Polly. He led investigators to her body, which he had buried in a shallow grave off Highway 101, near Cloverdale, California. He admitted to strangling her but did not provide a complete timeline of events leading to her death. Davis had hidden her body in thick brush and returned later to bury her.

On August 5, 1996, a jury delivered a death verdict against Davis. He made an obscene gesture at the camera after the verdict and later claimed that Polly had requested not to be harmed like her father. This claim was disputed and lacked evidence. Davis was formally sentenced to death, and although he survived an opiate overdose in July 2006, he remains on death row in California as of January 2024.