A former Catholic priest helped report a notorious abuser. Now he’s the one on trial.

Opening statements in the trial of a former priest accused of abusing a Catonsville Catholic school student in the 1990s included sharply different accounts on Monday about a case that divided Catholics across the region.

William Mannion Jr., who left the priesthood and later married, has been charged with multiple felony child abuse and sex offenses from his time at Baltimore County’s St. Agnes Church. He maintains his innocence.

The criminal trial underway in Circuit Judge Dennis Robinson Jr.’s courtroom is expected to last four days.

Dozens of Maryland priests have faced misconduct allegations since the state attorney general’s office began investigating the Archdiocese of Baltimore, culminating in a lengthy 2023 report detailing decades of “horrific and repeated abuse.”

Mannion, of Sparrows Point, left the priesthood in 1998, married and became a father. He started working at Johns Hopkins Bayview Medical Center as a case manager and later became a nurse in the psychiatric unit. The Vatican laicized him in 2004.

His supporters have tried to poke holes in the allegations against him, noting that he’s been an advocate for victims. He once helped bring down notorious child rapist John Joseph Merzbacher by reporting the former Catholic schoolteacher to church officials.

The attorney general’s office investigated Mannion but declined to include him on its list of more than 100 allegedly abusive priests. Mannion’s defense attorney Charles Waechter has said that this will be a foundation of his defense.

Prosecutor Lisa Dever, with the Baltimore County State’s Attorney’s Office, told jurors Monday that they will learn how a former altar server’s life was forever changed because of the abuse he suffered.

The Catholic faith and St. Agnes Church were central to the man’s identity as a child, she said. He attended church regularly with his family. The Banner is not naming the man because he says he is a survivor of sexual abuse.

Everything changed, the attorney said, when a “young, hip priest” named Father Bill joined the parish and started teaching at his school.

“He really liked Father Bill and thought he was cool,” Dever said.

But when the child answered a question incorrectly, Mannion would allegedly pull him out of class and sexually assault him in the nearby rectory where he lived with other priests, Dever said.

Sitting beside his defense attorney during the trial’s opening on Monday, Mannion gently shook his head as Dever described the alleged abuse in graphic detail. The prosecutor said Mannion would force the child to perform oral sex and then cover the boy’s head with the towel they used to clean up afterward.

Dever told jurors the abuse persisted for several years and only ceased when the man moved out of state. She said the man, who had been an athlete and Boy Scout, later struggled with drug and alcohol abuse and seemed unable to control his explosive anger.

“He could never keep anything straight,” she said. “His family was a hot mess.”

After keeping the alleged abuse secret for decades, the man reported it to the state attorney general’s office and later to his therapist, Dever said.

But Mannion’s defense attorney countered that the prosecution’s case has substantial problems.

“The dates in this particular case are very important,” attorney Christopher Luber stressed.

He said it was unlikely a young child could have been repeatedly removed from their elementary school classroom and returned disheveled after a midday sexual encounter without teachers or other school staff noticing or taking action to stop it.

Luber previewed testimony he expected from several former St. Agnes teachers and staff members who worked at the school in the 1990s and say the abuse Dever and the former altar server described never happened.

“Not one person notices anything?” Luber said. “That doesn’t add up.”

Luber also told jurors he will prove the victim’s memory should not be trusted. He said the man initially told investigators the abuse occurred in first, second and third grades and later said it happened in second, third and fourth grades.

In an interview before the start of the trial, Patrick Wall, a former Benedictine monk and clerical abuse expert, told The Banner that false claims against clergy are “highly uncommon” and that the man’s memory about the years the alleged abuse occurred could have been muddled.

Police initially said the child’s alleged abuse ended in 1994. But that’s the year Mannion joined the staff at St. Agnes, according to church assignment records and school yearbooks reviewed by The Banner. Prosecutors later said the misconduct stretched into 1995.

“Was William Mannion even there?” Luber asked.