Alstory Simon leaves the Jacksonville Correction Center as a free man. Picture: Seth Perlman / AP Source: AAP A MAN wrongly convicted of murder says a group committed to exonerating inmates put him in jail in the first place. In a case fraught with irony, it has been revealed that Alstory Simon, who was freed after serving half a life sentence last month, was coerced into confessing to the double murder he never committed by a group of freedom fighters in an effort to free another man. After he was placed at the scene of the horrific 1982 killing of two teenagers by the mother of one of the teenage victims, a drug-addled and desperate Simon was convinced he would be seen as guilty, and was told the only way he would avoid a death penalty would be to confess. Alstory Simon leaves the Jacksonville Correction Center as a free man last month. A vigilante group associated with Northwestern University, calling themselves the Medill Innocence Project, campaigned to have the man originally convicted of the murder, Anthony Porter, released - and for Simon to take his place on death row. Now two men have been convicted of this crime, and subsequently exonerated. But the question remains - who did it? In 1982 a teenage couple - Jerry Hillard and Marilyn Green - were shot dead at a pool in Washington Park in Chicago. Money and jewellery were stolen from the victims. With few reliable facts from witnesses, a man named Anthony Porter with links to local gangs with a record of robbery at the same location was identified as the primary witness. A stilted investigation led to six witnesses implicating Porter in the shooting, the Huffington Post reports. The mentally-disabled man protested his innocence, but after a short trial he was sentenced to death and denied an appeal. Sixteen years later, a group of journalism students took interest in the case as part of the Medill Innocence project. Simon in an undated photo, ageing in prison. Picture: Illinois Department of Corrections / AP Source: AAP Alstory Simon's 1999 mugshot. Picture: Chicago Tribune / AP Source: AAP The legal advocacy group affiliated with the Northwestern University was led by journalism professor David Protess. The particular part of the case they took to was a suggestion from one of the victim's mothers that another gang member, Alstory Simon, might be involved in the case. Hillard's mother said her son had been involved in a financial dispute with the man, according to the Huffington Post. Determined to free Porter, who would be executed for the crime, the group coerced a videotaped confession from Simon which saw Porter walk free and Simon sentenced to 37 ½ years in jail in 1999. Simon pleaded guilty, and tearfully apologised to Green's mother for accidentally shooting her daughter. Anthony Porter is released from prison in 1999. Picture: Beth A. Keiser / AP Source: AAP Simon was convicted of the crime just days before Porter was to be issued a lethal injection. The controversy prompted a statewide moratorium on the death penalty - ultimately sparing Simon himself from execution, Vox reports. Just as well, because a fresh investigation into the case, prompted by a documentary on the case released in New York last week, determined Simon's confession was false. In an interview with Fox News earlier this week, Simon described his new-found freedom as a huge relief. "It was like something that stepped completely out of me," he said. It's like when you have a big weight on your back and all of a sudden my body just got light. It was very hard to get long knowing the fact: that I was locked up in prison for something I knew I didn't do. Simon's release has opened up to more questions than answers in the more mysterious case. Not only does the question remain who is guilty of the murder, but the reason Simon was convicted is also unclear. It has been suggested that the Medill Innocence Project used Simon as a sacrificial lamb - framing him to free the man they had painted as an innocent victim. The Chicago Tribune reported that when Simon was found innocent, his defence lawyer Terry Elk argued his involvement in the case was politically motivated. "The system did work to free an innocent man, but he should never have been there in the first place," Elk said, going on to criticise the group that had him jailed. I think they essentially framed Alstory Simon to get Anthony Porter out of jail so they had that poster boy, and that should never occur. As for the question of who killed Jerry Hillard and Marilyn Green, it's unlikely the 32-year-old crime will be resolved. With two men now released 15 years apart, the likely prospect is that no one will face justice for the killings. Double jeopardy laws mean that Porter cannot retried for the same crime. Porter insists his innocence, and the Medill Innocence Project has been silent on the issue. Porter was released as prosecutors investigated another man's confession to the slayings that have kept Porter on death row for 16 years. He can't be tried again. Picture: Mike Fisher / AP Source: AAP