PORTLAND, Maine — The conviction of a man serving a five-year sentence for sexually assaulting a young relative in 1990 should be reversed and his client released because a key piece of evidence was lost, the man’s attorney, Stephen Smith of Augusta, told the Maine Supreme Judicial Court on Tuesday.

Clarence Cote, 66, of Nemaha, Nebraska, was found guilty in January 2014 on two counts of gross sexual assault on his niece, who was 8 years old at the time of the assault in 1990. He is incarcerated at the Maine State Prison in Warren, according to the Department of Corrections prisoner search website.

Susan Pope, assistant district attorney for Penobscot County who is handling the appeal, told justices the case “came down to a he said, she said,” and the jury believed the victim.

The victim, who now lives in East Millinocket, testified Cote sexually assaulted her several times, including in his truck when she went with him to deliver scrap metal in the Bangor area.

The woman said she had little contact with Cote after she moved and no contact with him after he moved to Arizona in 1992 or 1993.

She did not report the crime, but a family member who knew about the abuse told a school official, who called police, according to a previously published report. A police officer recorded an interview with her in 1994.

In 1996, the woman penned a letter to then-Gov. Angus King, asking him to help her “get justice,” Michael Roberts, deputy district attorney for Penobscot County, told jurors. King forwarded the letter to the Maine State Police. A warrant was issued in March 1996 for Cote’s arrest, but police were unable to find him because he had moved from Arizona, the last address family members had for him, to Nebraska.

Cote came to the attention of law enforcement in that state in April 2012, the prosecutor told the jury. Police in Nebraska noticed the 18-year-old warrant and let the Maine State Police know he was in custody.

When it came time for Cote’s trial, it was discovered a taped interview with the victim had been lost, which is why it could not be presented at trial.

The tape would have shown the girl talked to police about sexual touching but not the kinds of sexual assault she described as an adult at the trial, Smith told the justices.

“The recording addressed important inconsistencies in the complaining witness’s version of the offense,” he wrote in his brief. “Notwithstanding the lack of a statute of limitations, it is unfair and violative of due process to the defendant to allow conviction where the police lost vital evidence.”

Pope told justices the defense had the opportunity to cross-examine the victim and the police officer who interviewed her, who referred to his written report.

“We had the key piece of evidence in the case,” Pope said Tuesday. “We had the victim.”

The justices took the case under advisement.

There is no timetable under which they issue a decision.

To reach a sexual assault advocate, call the Statewide Sexual Assault Crisis and Support Line at 800-871-7741, TTY 888-458-5599. This free and confidential 24-hour service is accessible from anywhere in Maine. Calls are automatically routed to the closest sexual violence service provider.