Steven Avery was born in 1962 in Manitowoc County, Wisconsin, to Allan and Dolores Avery. Since 1965, his family has operated a salvage yard on the 40-acre (16 ha) property where they lived outside town. Avery has three siblings: Chuck, a younger brother Earl, and Barb (Barbara). He attended public schools in nearby Mishicot and Manitowoc, where his mother said he went to an elementary school "for slower kids". According to one of his lawyers in 1985, school records showed that his intelligence quotient (IQ) was 70, and that he "barely functioned in school".

In March 1981, at age 18, Avery was convicted of burglarizing a bar with a friend. After serving ten months of a two-year sentence in the Manitowoc County Jail, he was released on probation and ordered to pay restitution.

In late 1982, two men admitted that at Avery's suggestion, they threw Avery's cat "in a bonfire and then watched it burn until it died" after Avery had poured gas and oil on it. Avery was found guilty of animal cruelty and was jailed until August 1983. "I was young and stupid, and hanging out with the wrong people", Avery said later, of his first two incarcerations.

In July 1985, a woman named Penny Beerntsen was brutally attacked and sexually assaulted while jogging on a Lake Michigan beach. Avery was arrested after the victim picked him from a photo lineup, and later from a live lineup as well. Although Avery was 40 miles away in Green Bay shortly after the attack— an alibi supported by a time-stamped store receipt and 16 eyewitnesses—he was charged and ultimately convicted of rape and attempted murder, then sentenced to 32 years in prison. Appeals in 1987 and 1996 were denied by higher courts.

Around 1995, a Brown County police detective called the Manitowoc County Jail, saying that an inmate "had admitted committing an assault years ago in Manitowoc County and that someone else was in jail for it". The jail officer transferred the call to the Manitowoc County detective bureau. Deputies recalled Sheriff Kocourek telling them, “We already have the right guy. Don’t concern yourself with it.”

Avery's attorneys also discovered that an evidence box containing a vial of Avery's blood, collected in 1996 during his appeals efforts in the Beerntsen case, had been unsealed and a puncture hole was visible in the stopper. They speculated that the blood found in Halbach's car could have been drawn from the stored vial and planted in the vehicle to incriminate Avery; but FBI technicians tested the blood recovered from Halbach's car for ethylenediaminetetraacetic acid (EDTA), a preservative used in blood vials but not present in the human body, and found none. Avery's defense team presented expert witness testimony stating that it was not possible to tell if the negative result meant that EDTA was not present, or if the test itself was inconclusive.

Avery continued to maintain his innocence in the Beerntsen case. In 2002, after serving 18 years (the first six concurrently on the prior endangerment and weapons convictions), the Wisconsin Innocence Project used DNA testing—not available at the time of Avery's original trial—to exonerate him, and to demonstrate that Gregory Allen had in fact committed the crime. Allen, who bore a striking physical resemblance to Avery, had committed an assault at the same beach where Beerntsen was attacked in 1983, and was under police surveillance in 1985 due to his history of Criminal behavior against women; but he was never a suspect in the Beerntsen case, and was not included in the photo or live lineups presented to Beerntsen.

Avery was released on September 11, 2003. By that time, his wife had divorced him and he was estranged from his family. A court order had been issued limiting his contact with his children while he was incarcerated, citing physical and emotional abuse towards his wife and children. His wrongful conviction case attracted widespread attention. Rep. Mark Gundrum, Republican chairman of the Wisconsin Assembly Judiciary Committee, impaneled a bipartisan task force to recommend improvements to the state’s Criminal justice system aimed at decreasing the likelihood of Future wrongful convictions. Recommendations included a revamped eyewitness identification protocol and new guidelines for interrogations of suspects and witnesses and the collection and storage of material evidence. The recommendations were ultimately drafted into legislation that became known as the Avery Bill, which was passed and signed in October 2005, then renamed the Criminal Justice Reform Bill a month later after Avery was charged in the Halbach case.

Avery was arrested and charged with Halbach's murder, kidnapping, sexual assault and mutilation of a corpse on November 11, 2005. He had already been charged with a weapons violation as a convicted felon. Avery maintained that the murder charge was a frameup, promulgated to discredit his pending wrongful-conviction civil case. Although Manitowoc County ceded control of the murder investigation to the neighboring Calumet County Sheriff's Department because of Avery's suit against Manitowoc County, Manitowoc sheriff's deputies participated in repeated searches of Avery's trailer, garage, and property, supervised by Calumet County officers. A Manitowoc deputy found the key to Halbach's vehicle in Avery's bedroom. Avery's attorneys said there was a conflict of interest in their participation and suggested evidence tampering.

In March 2006, Avery's nephew, Brendan Dassey, was charged as an accessory in the Halbach case after he confessed under interrogation to helping his uncle kill Halbach and dispose of the body. He later recanted his confession, claiming it had been coerced, and refused to testify to his involvement at Avery's trial. Dassey was convicted of murder, rape, and mutilation of the corpse in a separate trial.

In pre-trial hearings in January 2007, charges of kidnapping and sexual assault were dropped. Avery stood trial in Calumet County in March 2007, with Calumet District Attorney Ken Kratz leading the prosecution, and Manitowoc County Circuit Court Judge Patrick Willis presiding. On March 18, Avery was found guilty of first-degree murder and illegal possession of a firearm, and acquitted on the corpse mutilation charge. Six weeks later he was sentenced to life in prison without possibility of parole on the murder conviction, plus five years on the weapons charge, to run concurrently.

In August 2011, a state appeals court denied Avery's petition for a new trial, and in 2013 the Wisconsin Supreme Court denied a motion to review the ruling. In January 2016, Chicago attorney Kathleen Zellner, in collaboration with the Midwest Innocence Project, filed a new appeal, citing violations of Avery's due process rights, and accusing officials of gathering evidence from properties beyond the scope of their search warrant.

After serving five years at the Wisconsin Secure Program Facility in Boscobel, Avery was transferred in 2012 to the Waupun Correctional Institution in Waupun.

On March 26, 2013, the public radio program Radiolab aired an episode titled "Are You Sure?" which featured a 24-minute segment entitled "Reasonable Doubt". It explored the story of Steven Avery from the perspective of Penny Beerntsen, the woman he was wrongfully convicted of sexually assaulting in 1985.

On December 18, 2015, Netflix released Making a Murderer, a ten-episode original documentary series which explores Avery's and Dassey's investigations and trials. The documentary "examines allegations of police and prosecutorial misconduct, evidence tampering and witness coercion." The series was widely reviewed and discussed in the media. It generated numerous follow-up interviews and articles with parties shown in the documentary, including family members, and some reporters of the trials.

A second petition, titled "Initiate a Federal Investigation of the Sheriff's Offices of Manitowoc County and Calumet County, Wisconsin", was submitted to petitions.whitehouse.gov on January 7, 2016. The petition was archived because it did not meet the minimum signature requirements.

On October 3, 2017, Avery's motion for a new trial was denied.