Sycamore, Illinois (CNN) A man wrongfully convicted of the 1957 murder of a little girl returned to a courtroom in his childhood hometown Thursday to ask a judge to clear his name for good.

When Jack Daniel McCullough was found guilty in 2012, prosecutors believed they'd solved the coldest case ever successfully tried. But Judge William Brady overturned the conviction a year ago and ordered McCullough released from prison after a new prosecutor said he couldn't have done it.

The judge dismissed the murder case but did so "without prejudice," leaving open the possibility that McCullough, who is 77, could some day be prosecuted again.

McCullough now wants the judge to prevent that by issuing a certificate of innocence, which also would strengthen his case as he pursues legal action and seeks compensation for the wrongful conviction.

In court Thursday, he denied having anything to do with the 1957 murder and explained why he is seeking the certificate: "I am innocent, proven innocent and I want my name back. My name has been in all the papers coast to coast. I've been put forward as a monster and people still believe I am a monster."

McCullough says accountability is his first priority, not money. "I would gladly pay with five years of my life if it means this doesn't happen to somebody else," he told CNN by phone as he made his way to Sycamore on Wednesday evening.

He added that the man who prosecuted his case, former State's Attorney Clay Campbell, is the one who deserves to be behind bars. Asked to comment earlier on the latest turn of events, Campbell said, "You know I have no comment."

Under Illinois law, McCullough is entitled to about $85,000 for the five years he spent behind bars. McCullough's attorneys are contemplating a lawsuit for civil damages as well.

In addition to McCullough, other witnesses Thursday included his former high school girlfriend and an expert on memory and eyewitness testimony.

The judge said he plans to issue his decision on April 12. Brady said he will consider FBI reports excluded from McCullough's trial that help establish his alibi.

While the decision could bring McCullough relief, the process has been excruciating for Charles Ridulph and Patricia Quinn, the surviving siblings of Maria Ridulph. The brown-eyed second-grader was 7 when she was snatched from a Sycamore street corner three weeks before Christmas. Her body was found 144 days later near the Iowa state line.

Charles Ridulph and Quinn have been a steadfast presence in court throughout McCullough's trial and related hearings; Quinn kept coming even when it became too painful for her brother. Quinn was in court Thursday, but her brother stayed home.

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.

"Sometimes you just want to stand up in court and scream," she said earlier this week as she waited to meet with the newly elected state's attorney, Rick Amato. The Ridulphs remain convinced of McCullough's guilt and believe a grave injustice is allowing him to get away with their sister's murder.

Lawyers at the DeKalb County Courthouse have long been divided over whether McCullough should have been charged. The physical evidence had been lost or destroyed, and many of the witnesses from 1957 are deceased.

The conviction began to unravel when one of the courthouse doubters, Richard Schmack, was elected state's attorney shortly after the trial. Knowing the case likely would come back on appeal during his time in office, Schmack took a close second look at thousands of pages of old FBI reports in the case file. He determined McCullough couldn't possibly have kidnapped Maria at the time police and prosecutors said he did.

Schmack concluded McCullough was making a collect call home and speaking with military recruiters at a US Post Office building in Rockford, some 40 miles away, when the child was kidnapped on December 3, 1957.

He filed his findings with the court under new ethics guidelines mandating that prosecutors take action when they believe someone has been falsely convicted. The law went into effect in January 2015.

A friendly stranger who said his name was "Johnny" lured Maria from the street corner by giving her a piggyback ride. A frantic search led by the FBI ended when she was found more than 100 miles from Sycamore, curled by a log in a cluster of trees along a highway popular with truckers.

McCullough, then known as John Tessier, had turned 18 the week before Maria vanished and was trying to enlist -- an effort that took him to Chicago on December 2 and 3, and then back to Rockford that evening and again the next morning.

The FBI checked out his alibi, verified a few details and cleared McCullough as a suspect in 1957. He passed a polygraph test and was inducted into the US Air Force 11 days after Maria went missing.

The mystery of who took Maria haunted Sycamore for more than half a century, and the prospect of a wrongful conviction leaves a sour taste among longtime residents of the semirural community about 70 miles west of Chicago.

Jack Daniel McCullough talks to reporters after his hearing in Sycamore, Illinois, on Thursday.

The Illinois State Police opened its investigation of McCullough in 2008 after one of his sisters 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.

Cheers filled the courtroom as soon as the judge, James Hallock, spoke the word "guilty" after four days of testimony. His pretrial rulings had stacked the deck against the defense by barring the 1957 FBI reports, which could have helped establish McCullough's alibi. Hallock, at the request of prosecutors, ruled the FBI reports were unreliable hearsay.

Like Campbell, the prosecutor who brought the McCullough case, Schmack held office for just one term. His work on the case contributed to his recent defeat at the polls. The office was represented at Thursday's hearing by his successor, Amato, and veteran prosecutor Stephanie Klein.

Amato is the fourth state's attorney in Sycamore to have handled a piece of the McCullough case. On Thursday, Judge Brady allowed the prosecution to cross-examine McCullough's witnesses.

Russell Ainsworth, who represented McCullough on behalf of the Exoneration Project, a legal clinic at the University of Chicago Law School, called three witnesses: McCullough; Janice Edwards Swafford, his high school girlfriend; and Nancy Steblay, a leading expert on memory and eyewitness identifications.

Swafford is recovering from back surgery, and arrangements were made for her to testify from her home in Florida via a remote video hookup. She has said police misquoted her in their reports, which she insists reflect "the opposite" of what she told them. She was brought to Sycamore for the trial but was never called to testify. Court papers filed on McCullough's behalf allege Swafford had been improperly hidden from the defense.

Police and prosecutors boasted they had solved the nation's coldest case when they won a conviction against McCullough. But doubts lingered about the evidence. Was it enough?

In court papers, the Exoneration Project rips the case apart -- including the timeline of events, an eyewitness identification and the testimony of three jailhouse informants.

Both Schmack and the Exoneration Project have raised the specter of possible police and prosecutorial misconduct. A special prosecutor is looking into perjury allegations in connection with a taped police interview of McCullough.

"There are serious issues with all of this evidence," the court filing on McCullough's behalf states.

Ainsworth believes police and prosecutors thought they'd cracked a "one in a million case." Prosecuting any case half-a-century old presents unique challenges. But, Ainsworth contends, when the pieces didn't quite fit, "the authorities started to put their thumb on the scale" to make their case stick.

"You have detectives who picked their perpetrator before they looked at all the facts, and then they tried to make the facts fit their perpetrator," Ainsworth added. "They turned everything on its head."

Like former prosecutor Campbell, Julie Trevarthen -- one of his top assistants at the time -- has declined to comment. The Illinois State Police, the lead investigative agency, said it can't comment on pending investigations or matters being litigated in the civil courts.

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

McCullough's attorneys contend that investigators buried evidence about a pay phone at the old Rockford post office that supported his alibi.

Illinois State Police investigators obtained records from the Rockford Park District, the current owner of the old post office building, the court document alleges. But even afterward, they continued to assert they didn't know the pay phone's number and suggested the call could have been placed from anywhere, the filing alleges.

The court filing asserts that McCullough's collect call home at 6:57 p.m. is nothing less than "an airtight alibi" that police and prosecutors "chose to ignore" because "it did not fit their theory of the crime."

McCullough's attorneys also took aim at the photo lineup used to gain the eyewitness identification at the heart of the case.

Maria had been playing a game of "duck the cars" with her best friend, Kathy Sigman Chapman, when 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.

Nearly 53 years later, in September 2010, investigators showed Chapman a photo lineup of six young men. She pointed to McCullough's picture and said it depicted Johnny, "to the best of my memory."

McCullough's attorneys say the lineup was suggestive and question whether an 8-year-old could really remember the face of a man she spoke with for just a few minutes half a century earlier.

Chapman declined comment, but an expert witness for the defense concluded that her memory was compromised by her age at the time she saw Johnny; the hundreds, if not thousands of photos she was shown; and the passage of more than half a century.

"Even a very confident and well-intentioned eyewitness can misremember and misreport the events of a crime scene and who was involved," Steblay wrote in a report filed with the court. "Memory is not like a video recorder. Instead, our memory of an event or a person is very malleable and is often unreliable."

Steblay pointed to 35 years of studies that show a 1-in-3 chance a lineup will produce a false identification if the person who committed the crime isn't included. People want to help, and they try to fill in the blanks. But instead of recognition, a person shown a lineup is far more likely to try to match a photograph with an image stored in his or her memory.

A child's perception and cognitive development further increase the likelihood of a false identification, Steblay's report stated.

Chapman was shown photographs of hundreds of suspects in the weeks and months after Maria went missing. Each time, her 8-year-old's memory was corrupted, Steblay concluded.

Chapman falsely identified a "filler" as the suspect in a lineup held in Madison, Wisconsin, 20 days after Maria disappeared. And she later said another suspect in another lineup seemed similar to "Johnny." On the witness stand, she testified she could not recall those events, and so the defense wasn't able to ask about them.

With those false identifications, Steblay said, Chapman's memory already was unreliable by late December 1957. The passage of five decades only dimmed it further.

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

The expert cited additional issues with the 2010 lineup. The investigator who displayed the photos knew the suspect's identity, a violation of widely accepted practices. A 2015 Illinois law requires "blind" lineups, meaning officers administering them can't know who the real suspect is.

Other issues resulted in a lineup unquestionably "biased against the defendant," Steblay said. The five "filler" suspects were shown in yearbook photos but not McCullough; he had left high school. Another photo of him was used in which the background was different, much darker.

In effect, Steblay concluded, the presentation made McCullough's photo stand out, increasing the risk of misidentification to a "strong likelihood."

Since McCullough's release, two inmates who testified about jailhouse conversations with McCullough have filed federal lawsuits against police and prosecutors, saying authorities failed to honor deals they made for the testimony. A third inmate was deported.

The informants' testimony, along with Chapman's eyewitness identification, were the two main pillars the judge cited in finding McCullough guilty.

A few weeks after McCullough's conviction, Schmack was elected state's attorney. He reviewed the 4,500-page file as McCullough's case moved through the appellate courts. He'd always had his doubts about the evidence, especially the Rockford alibi.

As he dug deeper, Schmack learned investigators had looked into the pay phone records but hadn't included what they learned in their reports.

He subpoenaed records from AT&T, which placed the pay phone's number inside the post office building, just as McCullough had said. The records only went back to the early 1970s. Still, he believed it was enough for him to conclude that McCullough's alibi held up, and that the FBI got it right when agents cleared him in 1957.