Steven Allan Avery was born on July 9, 1962, in Manitowoc County, Wisconsin, to Allan and Dolores Avery. The Avery family operated a salvage yard on a 40-acre property in the town of Gibson. Steven had three siblings: Chuck, Earl, and Barb. He attended public schools in Mishicot and Manitowoc, where he was noted to have learning difficulties, with an IQ of 70, and was enrolled in special education classes. In 1982, he married Lori Mathiesen, and the couple had four children before divorcing during his incarceration.​

Avery's early adult life was marred by legal troubles. In 1981, he was convicted of burglary and served ten months of a two-year sentence. In 1982, he was convicted of animal cruelty for dousing his cat in oil and gasoline and throwing it into a bonfire. In 1985, he was convicted of endangering safety after pointing a gun at a cousin.

On July 29, 1985, Penny Beerntsen was attacked while jogging along Lake Michigan. She identified Avery as her assailant, leading to his conviction for sexual assault and attempted murder. Despite having an alibi supported by multiple witnesses and a time-stamped receipt, Avery was sentenced to 32 years in prison. In 2003, DNA testing exonerated him, identifying Gregory Allen as the true perpetrator. Avery was released after serving 18 years.

Following his release, Avery filed a $36 million lawsuit against Manitowoc County and its officials for his wrongful conviction. In the midst of this legal battle, on October 31, 2005, Teresa Halbach, a photographer for Auto Trader magazine, disappeared after visiting the Avery Salvage Yard to photograph a vehicle. Her remains were later found on the Avery property.

Avery was arrested on November 9, 2005, and charged with Halbach's murder. His nephew, Brendan Dassey, was also implicated after confessing to assisting in the crime, though his confession was later contested as coerced. In 2007, Avery was convicted of first-degree intentional homicide and sentenced to life imprisonment without parole. Dassey was also convicted and sentenced to life in prison.

The case gained international attention through the Netflix documentary "Making a Murderer," which raised questions about the integrity of the investigation and potential misconduct by law enforcement. Avery's attorney, Kathleen Zellner, has filed multiple appeals citing new evidence and alleged violations of Avery's rights. As of 2025, Avery remains incarcerated, with ongoing efforts to secure a new trial.​