(CNN) Jack McCullough is innocent of the 1957 kidnapping and murder of a little girl and never should have been convicted, a judge ruled Wednesday.

By granting the 77-year-old military veteran a certificate of innocence, Judge William Brady cleared McCullough's name for good. The decision also returned the killing of 7-year-old Maria Ridulph in Sycamore, Illinois -- the coldest murder case ever tried -- to the unsolved case files.

"Based on the changes in the law and the consideration of the additional evidence now available to this court that may not have been available to the trier of fact ... Mr. McCullough's petition is granted," Brady said in issuing his ruling

When McCullough was found guilty in 2012, spectators who filled the courtroom raised a boisterous cheer. But just a year ago, Brady overturned the conviction and freed McCullough after new evidence surfaced supporting his alibi.

At the time, Brady left the door open for a new prosecutor to refile the charges. Wednesday's ruling firmly shuts that door -- and makes it easier for McCullough to seek compensation for his false conviction and five years behind bars.

"I'm innocent and I didn't want there to be any doubt," McCullough said, explaining why he asked the court to declare him innocent. "What was done to me was criminal. They knew I was innocent and they put me in prison anyway."

His status as a former police officer convicted of killing a child made him a target behind bars, he said.

"You don't have a life," he explained. "Your life is in danger every second that you're in prison. I'm lucky to have survived prison."

McCullough's civil rights lawyer, Russell Ainsworth, said: "There is no way to take what happened to Jack McCullough and square it with any legitimate investigation. He was innocent. Everybody knew he was innocent and yet they pursued the investigation."

Read the original series on the case: 'Taken' Maria Ridulph's murder went unsolved for half a century. Then detectives pursued a tip, and a man was brought to trial and convicted in the 1957 murder of the 7-year-old in Sycamore, Illinois. Now that man is free. Ann O'Neill's 2013 series on the case, "Taken," raised questions about whether the trial was unfairly one-sided.

Ainsworth has handled several cases for The Exoneration Project , a clinic at the University of Chicago's law school. He described Illinois as "an epicenter for wrongful convictions" and called for reform, including stronger police oversight.

"It has to stop," he said. "We want, through Jack McCullough's struggle, for other people to learn that this can happen in our society. This is not part of bygone years and what happened in the '70s and '80s. This is happening today. This is happening to people who are honest, law-abiding citizens."

Two big changes in the law were enacted after McCullough was convicted in 2012.

In 2015, it became a prosecutor's ethical duty to point out wrongful convictions and do something about them. This resulted in a report by prosecutor Richard Schmack outlining why McCullough couldn't have committed the crime. And in 2016, the law was changed to allow expert testimony, such as that offered in court last week by an eyewitness identification expert.

For Maria's surviving siblings, now in their 60s, Wednesday's ruling was another in a series of painful days in a case long marred by missteps and false hopes. They had been convinced that McCullough was the killer and now believe a grave injustice is allowing him to get away with their sister's murder.

"It's been horrid, more horrid than when she was taken," Maria's sister, Patricia Quinn, said last week outside the courtroom. "At this point we just want to stand up and shout for all it's worth." Her brother, Chuck, grew so disheartened he stopped attending the court hearings.

The Illinois State Police investigators and prosecutors responsible for McCullough's conviction did not respond to requests for comment, and have said in the past that they can't discuss matters that could wind up being litigated in court.

Jack McCullough testified that he wanted to clear his name because people still saw him as a monster.

A special prosecutor is looking into whether a police interrogation tape and other evidence may have been deliberately concealed from McCullough's defense. And an investigation into another suspect remains open, even if it may not result in charges being filed.

Illinois State Police opened their investigation into McCullough in 2008 after one of his sisters reached out to a tip line and said their mother had accused him on her deathbed: "Those two little girls and the one who disappeared, John did it," the sister quoted their mother as saying.

Many of the players returned last week to the stately Classical Revival-style courthouse in Sycamore. Brady heard testimony from three witnesses but postponed announcing his decision until Wednesday -- nearly a year to the day since he freed McCullough from an Illinois prison.

The turn of events came at the urging of former State's Attorney Richard Schmack, who took a second look at the case. He determined McCullough could not have committed the crime because he was 40 miles away at a military recruiting station in downtown Rockford at the time Maria vanished from a street corner in Sycamore.

Schmack said he was obliged to look into a conviction he doubted and file his findings with the court under ethics rules that went into effect in 2015. When he began his inquiry, Schmack suspected McCullough had been unfairly convicted. But by the time he finished, Schmack was convinced McCullough was innocent.

Schmack was elected shortly after McCullough's trial and has since been voted out of office. Rick Amato, the newly elected State's Attorney, did not dispute Schmack's findings.

McCullough becomes the 786th convicted killer exonerated in the US -- and the 122nd in Illinois -- since advances in DNA analysis launched the modern innocence movement in 1989, according to the National Registry of Exonerations. The registry, now maintained at the University of California at Irvine, is considered the most complete record of overturned false convictions.

Attorney Russell Ainsworth, who represented McCullough on behalf of The Exoneration Project, goes over the crime timeline in court.

Although DNA was not involved in McCullough's case, the certificate of innocence qualifies him for compensation from the state of Illinois for the five years he was confined and strengthens his ability to seek damages through civil lawsuits.

Besides finding McCullough was wrongly convicted, Schmack uncovered disturbing evidence pointing to possible misconduct and evidence manipulation. Evidence beneficial to McCullough was buried, ignored and perhaps concealed deliberately, he found.

As McCullough's lawyer Ainsworth phrased it, authorities "put a thumb on the scale" to win the conviction. Ainsworth, a civil rights attorney with a prominent Chicago firm, helped McCullough restore his good name, but another Chicago civil rights lawyer, Gabriel Fuentes, won his release.

Court records made public after McCullough's conviction show that police and prosecutors received the FBI's full archive in June 2010 -- more than a year before McCullough's arrest. By then, Schmack concluded, they "knew or should have known" there was ample evidence pointing to McCullough's innocence.

McCullough simply wants to get on with his life.

"I am innocent, proven innocent, and I want my name back," he testified last week. "My name has been in all the papers coast to coast. I have been put forward as a monster, and people still believe I am a monster."

McCullough denied having anything to do with Maria's kidnapping and murder.

"He has spent the last six years fighting to clear his name," Ainsworth told the judge. He argued that the three pillars holding up the conviction -- the prosecution's timeline, a lineup identification from the only eyewitness, and testimony from three "incentivized" jailhouse informants -- each had crumbled under close scrutiny.

Judge William Brady talks during McCullough's certificate of innocence hearing.

And, FBI reports that had been barred from the criminal trial finally entered the case record with McCullough's petition for a certificate of innocence. They document the frantic search for Maria the night of December 3, 1957; statements by some two dozen witnesses establish she was likely taken sometime between 6:45 and 6:55 p.m.

The reports show that Maria was seen and heard at a time when her father and neighbors were still watching "Cheyenne" and "Name That Tune" -- half-hour television shows that began at 6:30. At the trial, prosecutors avoided mentioning a specific time but left the impression Maria was snatched closer to 6 p.m.

The FBI reports also establish that McCullough, then known as John Tessier, was questioned and cleared by the FBI within days of Maria's disappearance. His alibi checked out, including a collect call home for a ride from Rockford at 6:57 p.m. and conversations with military recruiters at the Rockford Post Office between 7:15 and 7:30 p.m.

"Nothing else matters if Mr. McCullough was in Rockford at the time," Ainsworth said. "All of the other evidence falls away. He simply could not have committed this crime."

The exoneration hearing also featured testimony from McCullough's high school sweetheart, Janice Edwards Swafford. Speaking via a remote hookup from her home in Florida, where she was recovering from surgery, she said she believes he came to the door of her home at about 9:30 that night. He was about half an hour late, she recalled, and excited that he had passed his physical.

She said she'd been willing to testify at McCullough's trial in September 2012 and had been brought to Sycamore by prosecutors but was never called.

She said she was sure he had been to the induction center in Chicago that day, but couldn't recall the specific date.

"He was really, really excited about passing the physical," she said. He did not seem jumpy or nervous or out of sorts, she added. "He was happy. He wasn't anything else. He was just the same old guy."

She said he asked her to wait for him until he returned from his hitch in the US Air Force. She said she couldn't wait.

"I was only 17, and I wasn't ready to get serious."

Clay Campbell was the prosecutor who brought the case against Jack McCullough.

McCullough's lawyers also presented lawsuits filed by two of the three inmate witnesses who testified against McCullough in 2012. Both said they were promised favors for their testimony and filed suit when those promises weren't kept.

An expert in eyewitness identifications attacked the third prong of evidence supporting the conviction -- a photo lineup ID by the surviving witness, Kathy Sigman Chapman.

Chapman was playing in the snow with Maria, her best friend, at a Sycamore street corner when, she said, a friendly stranger approached, gave his name as "Johnny" and took Maria on a piggyback ride. Chapman, then 8, went home to fetch her mittens. When she returned, Johnny -- and Maria -- were gone.

Nancy Steblay, a psychology professor at Augsburg College in Minnesota, studies the role of memory in eyewitness identifications. She shook her head and said she strongly doubted that after 52 years Chapman could reliably recall the face of a man she saw for a few minutes under poor lighting when she was 8.

"It's just too long," she explained. "You get a really brief glance at the individual in very poor illumination and you're going to try to remember that 52 years later?" she said, her tone incredulous.

She said the pressure and "constant barrage" of mug shots and lineups shown to Chapman in the weeks following the kidnapping finally led her to falsely identify a man who looked nothing like the descriptions she gave of "Johnny." By then, her memory had been so polluted by outside influences that it could be considered unreliable.

The lineup shown by state police was highly suggestive, Steblay added. Only McCullough's photo, the one she selected, was not taken from Sycamore's high school yearbook. McCullough had left high school, so another photo of him was used; he wore no tie, his collar was open, and the background was much darker.

Also, Steblay testified, the officer displaying the photo lineup knew who the suspect was. That is no longer considered an acceptable practice.

And, lastly, Steblay said Chapman's identification came after she eliminated several photos and then compared two, side by side. That was a sure sign the identification was made not from memory, which is instant, but rather through a process of elimination and matching an image closest to the image in her memory.

"Based on the scientific research, I would not say this was a reliable lineup," Steblay concluded. Asked to elaborate, she said the passage of 52 years jumped out at her the most.

"Oh, boy. Just kind of based on the lineups I have known, this is very bad," Steblay said. "This was a very bad one. I don't have confidence in this identification."