Gerry Thomas, 62, was exonerated Monday after spending nearly 30 years in prison for the attempted murder of a Detroit, Michigan woman in 1987.

Thomas was convicted and sentenced despite no physical evidence linking him to the crime. His identification as a suspect was based solely on the testimony of one witness two years after the crime took place.

Throughout the course of his sentence, Thomas maintained his innocence and hoped to be freed. “I am thankful and so happy to finally be going home to my family,” he told reporters Monday.

The exoneration was the outcome of an investigation by the Conviction Integrity Unit of the Wayne County Prosecutor’s Office. The investigation itself was made at the request of the Innocence Project, a group founded in 1992 whose actions have so far led to 189 DNA-based exonerations.

In 1987, a Detroit woman was sitting in her car waiting for her son to come out of a convenience store when a man brandished a knife and forced her to drive away from the store. The assailant then raped the woman before she was able to escape. The assailant then drove away with the victim’s car after she fled the scene.

Three weeks after the crime took place, police found the stolen vehicle and detained the driver and the passenger, neither of whom were the assailant, according to the victim. The driver said he received the car from his brother. Despite the fact that the brother matched the description of the assailant given by the victim, police did not conduct any further investigation into the driver’s brother.

An investigation was resumed two years later when the victim told police she believed that she spotted the assailant emerging from a convenience store not far from the initial crime scene. The person in question was Thomas, whom police found eating at a nearby Burger King. Thomas was arrested and charged in May 1990. The police allegedly did not conduct any further investigation of the incident during the intervening nine months.

Thomas was found guilty of criminal sexual conduct, armed robbery and assault with intent to murder in 1991 and was sentenced in 50 to 75 years in prison. This was despite the fact that Thomas had an alibi and the jury was not told that the victim’s vehicle registration information had been located at the home of the driver’s brother, a man who more closely matched the initial description given by the victim.

As of 2016, more than 2.3 million people were incarcerated in the United States. The country is the third largest in the world by overall population but is the largest by far in terms of the number of people incarcerated. While the present population of the US is 4.25 percent that of the entire world, nearly one in four prisoners internationally currently reside in the US incarceration system.

Research by the Innocence Project indicates that between 2.3 percent and 5 percent of all US prisoners are actually innocent, meaning that up to 115,000 individuals languish in US jails completely innocent of the crimes they were accused of committing. In addition to the prison population, an additional 4.75 million US adults were on probation or on parole as of 2013, meaning that 2.8 percent of the US adult population, or nearly 7 million people, was on probation, parole, in jail or in prison.

One of the individuals cleared by the Innocence Project is Darryl Hunt. A North Carolina resident, Hunt was wrongfully convicted for the rape and murder of a newspaper copy editor and sentenced to life imprisonment. Hunt, a black man, was sentenced for the crimes against Deborah Sykes, a white woman.

After he was convicted in the Sykes case, Hunt was tried in 1987 for the murder of 57-year-old Arthur Wilson of Winston-Salem, North Carolina. Both cases were overturned on appeal in 1989, however Hunt was tried again on the Sykes charges in 1991 and was convicted.

DNA testing of the existing physical evidence was conducted in 1994 showing that Hunt could not have been involved in the rape of Sykes at the time. A Forsyth County judge, however, ruled that the DNA evidence was not sufficient to gain an acquittal. Hunt languished in prison until 2004 when he was fully exonerated after spending 19 and a half years behind bars.

Hunt went on to work as a volunteer with the national Innocence Project and created the Darryl Hunt Project for Freedom and Justice, devoted to “educating the public about flaws in the criminal justice system and working for reforms to criminal laws in North Carolina.” Hunt’s struggle with the criminal justice system exacted an immense physiological and psychological toll. Hunt became terminally ill and after bouts of depression reported by his friends, he died from a self-inflicted gunshot wound in 2016.

Individuals fortunate enough to exit prison find it extremely difficult to find employment, procure decent housing, obtain non-usurious loans and otherwise are denied access to a host of other social services.

Most of those cleared of wrongdoing through the efforts of the Innocence Project, which has a yearly budget of less than $20 million to investigate wrongly incarcerated individuals across the entire US judicial system, were facing life imprisonment or even execution.

Moreover, in addition to funding challenges, the project and others like it face significant legal hurdles. In a 2009 case brought before the US Supreme Court, District Attorney’s Office for the Third Judicial District v. Osborne, the court decided that the Constitution’s due process clause did not require states to turn over DNA evidence to a party seeking a civil suit even if the evidence involved may ultimately be exculpatory.

The majority opinion argued that convicted felons had “no constitutional right to obtain post conviction access to the State’s evidence for DNA testing.” At the time, Chief Justice John Roberts essentially argued that unrestricted access to forensic evidence by claimants and their attorneys would pose an unacceptable challenge to the criminal justice system. Post-conviction DNA testing, according to Roberts, risks “unnecessarily overthrowing the established system of criminal justice.”