Speaking quietly but firmly, a 24-year-old man testified for more than two hours Tuesday about enduring a series of childhood sexual assaults by two Catholic priests and a teacher, all of whom worked at a church and middle school less than a mile from his Northeast Philadelphia home.

The molestation began in the late 1990s when the man was a 10-year-old altar boy at St. Jerome's, a Catholic school near Pennypack Park, and left him overwhelmed by fear, guilt, and shame, he testified in Common Pleas Court. In his family and community, priests and nuns were given unquestioned authority, he said, and it would be years before he told anyone he had been abused.

"I was scared, I was embarrassed," said the man, who was identified in a grand jury report as "Billy Doe." The Inquirer does not identify alleged victims of sexual assault. "I was afraid I was going to get in trouble. I thought I did something wrong."

After the assaults, Billy testified, he stopped seeing his friends, dropped out of most clubs and sports teams, and was expelled from two high schools. Within five years, he went from smoking marijuana to trying pills and hard drugs and, eventually, he said, developed a "full-blown heroin addiction."

Billy's alleged assailants, the Rev. Charles Engelhardt, 66, and Bernard Shero, 49, watched the testimony from across the room, at times glancing down at the table in front of them.

Another priest, the Rev. Edward Avery, has pleaded guilty to assaulting Billy in 1999 while living at St. Jerome's rectory. Avery is expected to testify, possibly as early as Wednesday.

Engelhardt and Shero are the last two of five people charged as a result of the 2011 county grand jury report outlining a cover-up of clergy sexual abuse of children in the Archdiocese of Philadelphia. The accuser's 2009 complaint led prosecutors to file charges against church officials and higher-ups, including the Rev. William J. Lynn, who handled priests' assignments for the archdiocese. Lynn was convicted last year of child endangerment and is serving time in prison.

In their opening statements this week, defense attorneys portrayed Billy as opportunistic and drug-addled, saying he "never told the same story twice" and suggesting that recent sex-abuse scandals have left the church vulnerable to false accusers. They are expected to spend much of Wednesday cross-examining Billy, who has been in and out of jail and in almost two dozen rehab programs since he was 14.

A slightly built man with dark, close-cropped hair and a goatee, Billy testified Tuesday that he had been sober for a year. He said he was an outgoing child who played sports, got good grades, and had plenty of friends.

As an altar boy, Billy sometimes assisted the priests with preparing for the daily Mass, and one day after an early-morning service, he said, Engelhardt caught him drinking the leftover sacramental wine. Instead of scolding him, he said, Engelhardt offered him more wine and asked him about himself, questions such as whether he had a girlfriend and if he ever looked at pornography.

Engelhardt then showed him several pornographic magazines, told him it was time for him to become a man, and said their "sessions" would start soon. A week or so later, he testified, Engelhardt asked him to stay after Mass and sexually assaulted him in a church sacristy.

"He told me God loves me, that it was going to be OK," Billy said. "He said, this is what God wants."

Billy avoided Engelhardt after that, but said Avery targeted him some months later in the spring of 1999. Avery told Billy he had talked to Engelhardt about their "sessions," Billy said, and assaulted him twice over a period of about a month.

The next school year, Billy testified that Shero, his sixth-grade homeroom and English teacher, offered him a ride home. Instead, he said, Shero drove him to Pennypack Park and assaulted him in his car.

The first time Billy ever spoke of being molested was in an impulsive confession to his best friend in high school, he testified, when the two were sophomores. They were discussing a teacher they found "creepy" because of the way he hugged his students and stood overly close to them, and Billy said he told his friend why he was so bothered by it.

The friend, Leo Hernandez, testified Tuesday that he felt angry after Billy's confession, but that the two did not speak much more about it. Hernandez never told anyone for fear of betraying Billy's trust, he said.

"I'm pretty sure it's not too easy to tell a guy that you were touched," he said. "It's hard for me to talk about it in front of all these people, so I can only imagine."