PLATTE CITY, Mo. (AP) — A single bullet recovered from the liver of a shooting victim helped convict Mark Woodworth of his neighbor’s 1990 shooting death. Now the northwest Missouri man says a private detective tampered with that evidence and wants a judge to toss it out as a third murder trial looms.

Woodworth returned to court Monday in Platte County, two months after the Missouri Supreme Court tossed out his most recent conviction and one month after a judge released him on bail pending a new trial. Platte County Circuit Judge Owens Lee Hull Jr. didn’t immediately rule on the request to exclude the ballistics evidence or several other defense motions but said he expects to do so by early April.

Defense attorney Bob Ramsey didn’t mince words when questioning how the bullet surgically removed from Lyndel Robertson wound up with a British ballistics expert retained by private investigator Terry Deister, who was hired by Robertson’s family but wound up leading a Livingston County Sheriff’s Office investigation that had stalled two years after the shooting. Lyndel Robertson’s wife, Cathy, was shot to death while the couple slept in their Chillicothe home.

‘‘They framed Mark Woodworth,’’ the defense lawyer said. ‘‘And it’s as plain as day.’’

Assistant Attorney General Ted Bruce countered that the supposedly new evidence submitted by Woodworth had already been covered in previous court proceedings. And after the hearing, one of the Robertsons’ five children called the defense theory ‘‘nonsense.’’

‘‘It’s completely ludicrous to think he was framed,’’ said Rhonda Oesch, the oldest child in the family home when her parents were shot more than two decades ago.

Woodworth had been sentenced to life in prison. He was first convicted in 1995 and then briefly released after a successful appeal before a second jury convicted him in 1999.

A former St. Louis County detective now working as a forensics consultant testified Monday that a crime scene photo of the bullet looked different than how it was described by the doctor who removed it. He also described a gap in the bullet’s chain of custody that he said raises questions about the integrity of the investigation that led to Woodworth’s conviction.

‘‘It could be the same bullet. It could not be,’’ said defense witness Daniel Jackson. ‘‘There’s a four-day gap in the chain of custody.’’

Ramsey also questioned the recent courtroom conduct and previous role in the case played by Livingston County Circuit Judge Brent Elliott, who was an opposing attorney in a juvenile court hearing in which Woodworth was certified to stand trial an adult. Woodworth was 16 when Cathy Robertson, the wife of his father’s business partner, was killed.

Cameron attorney Michelle Puckett-Burkhead has accused Elliott of destroying documents in two unrelated criminal cases from 2012 and threatening a county clerk with arrest if she defied him. She recently joined Woodworth’s defense team.

Elliott has declined to discuss his involvement in the Woodworth investigation, citing restrictions on pending criminal cases. His role was previously questioned in a May 2012 ruling by a Boone County judge who noted that Elliott had also represented the first trial judge in Woodworth’s case, and Robertson’s eldest daughter in other legal matters.

Woodworth’s defense team submitted a 1992 case log from Deister showing that the private investigator and a Livingston County deputy regularly consulted on the case. Ramsey suggested the trio colluded to set up his client.

The court filing also includes an October 1992 letter from Deister to a British firearms expert in which he outlines a desire to ‘‘take whatever steps necessary, within reason, to identify this weapon.’’

Five defense witnesses testified Monday, including current Livingston County Sheriff Steve Cox, who reopened the case several years ago as questions surrounding Woodworth’s guilt mounted. Cox said former deputy Sheriff Gary Calvert and Deister failed to fully investigate several leads that could have implicated another suspect, the abusive ex-boyfriend of the Robertsons’ oldest daughter.

Clinton County Clerk Molly Livingston, an alternate juror at Woodworth’s first trial, testified that she continued to discuss her belief in Woodworth’s guilt even as the case was under review by the state’s highest court. Ramsey leveraged that testimony to help persuade Hull to transfer the court file to Platte County.

Boone County Circuit Judge Gary Oxenhandler, who was appointed by the state Supreme Court in an advisory role, ruled that Woodworth was the victim of ‘‘a manifest injustice.’’ He concluded that ‘‘there was nothing fundamentally fair about the investigation of the Robertson crimes, or in turn, Woodworth’s prosecutions and convictions for those crimes.’’

Oxenhandler determined that state prosecutors failed to provide Woodworth’s attorneys with copies of letters that casted doubt on Woodworth’s guilt. The letters were between the Livingston County trial judge, state and local prosecutors and Lyndel Robertson.

The letters were first publicly disclosed by The Associated Press in 2009 as part of an investigation into the Woodworth case and Hulshof’s prosecutorial record.

Before adjourning Monday, the judge gave Woodworth permission to cross the state line for a two-day visit with his grandmother later this month near Quincy, Ill.