Lawyers for a priest and a former parochial-school teacher attacked the credibility Wednesday of a 24-year-old Northeast Philadelphia man who says the pair sexually assaulted him when he was a 10-year-old altar boy.

The witness - The Inquirer does not identify victims of alleged sexual assault - was questioned for almost four hours by lawyers for the Rev. Charles Engelhardt and Bernard Shero.

On Tuesday, the witness told the Common Pleas Court jury that serial sexual assaults by Engelhardt, another priest, and Shero while he was a fifth grader at St. Jerome's parish school shattered his childhood and propelled him into a life of petty crime and drug addiction.

Defense attorneys Burton A. Rose and Michael McGovern argued that the assaults never happened.

Rose, representing Shero, showed witness and jury blowups of the man's report cards from fifth through eighth grades. Rose noted that his grade average went from 88.6 to 80.7 and his attendance barely changed during the time of the alleged assaults in 1998 and 1999.

"So you went to school the next day after this man [Shero] anally raped you in the back of his car?" Rose asked.

"It was school, I had to go," replied the witness, identified as "Billy Doe" in the 2011 county grand jury report.

The witness said the report cards did not reflect the many days he left early because he felt ill, or the hours spent in the school nurse's office.

Rose pondered aloud why the witness let himself be serially raped by two priests and a teacher. Rose reminded the witness that he allegedly ended a second attempted assault by Engelhardt by "threatening to kill him if he touched you again?"

"Why did you get into his [Shero's] car? . . . You could see what was about to happen?"

Maintaining his flat, clipped answers, the witness replied that he was only 10 and was afraid to tell anyone about the assaults by the priests or Shero, his homeroom and English teacher.

McGovern questioned why the witness waited 10 years before contacting archdiocesan officials about the alleged assaults.

He also asked why the witness remembered details of the assaults but not what he told church investigators on Jan. 30, 2009.

The witness insisted that when he finally contacted the church hotline, after breaking down during a drug-counseling session, he was still under the influence of drugs: "I don't remember the conversation. I was not mentally there."

The jury also heard from the witness' father, a Philadelphia police officer, who described how his "fun-loving" younger son became more withdrawn and a user of drugs, going from marijuana to prescription narcotics to heroin and through more than a score of rehab facilities.

Shero, 49, and Engelhardt, 66, are on trial for the alleged assaults on Billy. The other priest, Edward Avery, now 70, pleaded guilty last year shortly before he was to go on trial with two other priests in the investigation of clergy sex abuse of children in the Archdiocese of Philadelphia.

Avery, now defrocked and serving 21/2 to five years in prison, is expected to testify Thursday.

The pair are the last two of five people charged as a result of the 2011 county grand jury report.

Last year's landmark three-month trial ended June 22, when the jury found Msgr. William J. Lynn guilty of child endangerment, the first church administrator convicted for a priest's sexual abuse of a child.

Lynn, 62, who as secretary for clergy from 1992 to 2004 was responsible for investigating allegations against priests, was sentenced to three to six years. He is in a state prison and appealing his conviction.

Contact Joseph A. Slobodzian at 215-854-2985, jslobodzian@phillynews.com, or @joeslobo on Twitter.