A man serving a 65-year sentence for the murder of Indiana University student Jill Behrman, whose remains were found near Bloomington almost 20 years ago, could be freed from prison because of several “serious mistakes” his attorneys made during the 2006 trial.

Indianapolis U.S. District Court Judge James Sweeney on Monday vacated a murder conviction against John Myers II. Myers will be released from custody unless the state elects to retry him. The state must make that decision within 120 days of the Sept. 30 judgment, according to court documents.

It is unclear whether Myers will face a new trial. The state attorney general's office on Tuesday said in a statement it "respectfully disagrees" with the decision and it will "vigorously pursue justice," but did not elaborate on what that means.

What we know: Jill Behrman's death and John Myers' conviction

In a lengthy decision rebuking Myers' trial counsel — which consisted of Indianapolis-based attorneys Patrick V. Baker, Hugh Baker and Mike Keifer, with Patrick Baker and Hugh Baker defending Myers at trial — the court said that a new trial would come at "considerable cost" to not just the state, but more importantly to Behrman's family.

Marilyn Behrman, Jill's mother, was still reeling from the decision when IndyStar reached her on Tuesday afternoon. She said she's "disappointed" by the decision.

“I’ve always believed that (Myers) was responsible," she said.

Sweeney found that Myers received ineffective assistance of counsel at his trial, a violation of his Sixth Amendment rights. While the court did not concur with all of Myers' arguments, it agreed that Myers' counsel made false statements to the jury during opening arguments — something that the lead attorney on Myers' case, Patrick Baker, reportedly admitted to during an attorney disciplinary proceeding — and failed to object to evidence that should not have been presented to a jury.

"In the end," the decision said, "these serious errors all but destroyed the defense that trial counsel presented to the jury and tainted the entire trial."

Timeline: Jill Behrman's case

Patrick Baker did not address the errors in Sweeney's decision when reached by IndyStar. Baker said he and his legal team still believe Myers is innocent, and that Sweeney's decision gives Myers and his family "renewed hope."

Morgan County prosecutor Steven Sonnega said it is too early to discuss the next step in the case, but added he is disappointed with the decision to vacate Myers' conviction. Sonnega said he is in contact with Behrman's parents and the lead investigator of the case, who is now retired.

Murder verdict challenged

Behrman, an IU freshman, went for a morning bike ride north of Bloomington on May 31, 2000, and never came back. Her skeletal remains were discovered in 2003 in a remote Morgan County field about 15 miles from Bloomington. Authorities determined she died from a shotgun wound to the head, according to court documents.

Investigators concluded that Myers, who lived in Ellettsville, a town about seven miles from IU's campus, killed her out of anger over a failed relationship with a girlfriend. A jury convicted him of murder in 2006, later sentencing him to 65 years in prison.

Myers tried multiple times to challenge his conviction locally, making the same argument he made in federal court: that his attorneys made several mistakes that prejudiced the jury against him. But the state appeals court and a Morgan County judge rejected his arguments. And the Indiana Supreme Court denied Myers' request to review his murder conviction, the Associated Press reported.

In 2016, Myers filed a petition for a writ of habeas corpus, which means a person is seeking relief from a conviction or sentence imposed upon them at the state level. Chief Federal Defender Monica Foster wrote in the petition that Myers made a "credible claim of innocence."

She also said there were some "serious and compelling allegations of misconduct" by Myers' trial counsel.

'False' statements at trial

Myers called out his defense team for opening the trial with false statements that the attorneys used to push a theory pointing to another killer.

The theory claims that Behrman was in a romantic relationship with her supervisor, whom she worked for at the Student Recreational Sports Center, and that the man killed her after she became pregnant.

The defense said that shortly after Behrman disappeared, a tracking dog was sent to the man's home. But police, who allegedly wanted to cover up his involvement, pulled the dog away, according to court documents. They also said that Behrman and the man were "seen arguing days before she disappeared."

"They sent dogs out. They sent dogs out right after the disappearance on May 31st," Patrick Baker said, per the court decision. "You’ll hear from (Det.) Tom Arvin that a dog followed a scent, went to a home of a coworker. Did he go inside? No. He pulled the dog off."

But in the federal opinion, Sweeney says the defense's assertions are false.

Court documents show that in 2011, Patrick Baker was disciplined by the Indiana Supreme Court for saying that a dog was alerted to the man's home but was called off.

"These statements were false and (Baker) should have known that no evidence would be admitted at trial to support them," the Supreme Court statement said.

Court: Defense didn't challenge assault motive

Myers also argued that his attorneys didn't object to testimony from a forensic pathologist that Behrman was raped before she was murdered.

Despite determining that there was no physical evidence to support the rape claim, the Indiana Court of Appeals didn't think that the testimony prejudiced the jury against Myers. The federal court disagreed, finding that the testimony helped the state establish a motive.

"The rape evidence was the only evidence that allowed the jury to make sense of why Myers would have randomly murdered a stranger riding a bicycle near his residence," the court said. "The state was able to use the rape evidence to argue in closing that Myers’s motive was 'clear'—rape is a “crime of control,” and since he could not control his ex-girlfriend, he used rape to control Ms. Behrman, who was “at the wrong place at the wrong time."

IndyStar reporters Andrew Clark and Vic Ryckaert contributed to this report.

Contact IndyStar reporter Crystal Hill at 317-444-6094 or cnhill@gannett.com. Follow her on Twitter: @crysnhill.