Even among the horrors cataloged in the Philadelphia grand jury report on child sexual abuse by Roman Catholic priests, the story of "Billy Doe" stands out.

He was the 10-year-old altar boy and fifth grader at St. Jerome's parish in the Northeast allegedly serially molested and raped by two priests and a teacher who, prosecutors said, passed him from one abuser to the next.

Ashamed and too frightened to tell anyone, Billy, now 23, got ejected from two high schools, tried to kill himself, and spent years addicted to heroin and pills. Billy Doe is a pseudonym used by prosecutors; The Inquirer has a policy of not identifying victims of sexual assault."

On Tuesday, two of Billy's alleged victimizers go to trial in Philadelphia Common Pleas Court in a coda to this year's landmark trial that ended in the first conviction of an archdiocesan leader for the sexual abuse of a child by a priest.

Msgr. William J. Lynn was convicted June 22 on one count of child endangerment involving the assault on Billy by the Rev. Edward V. Avery in the 1998-99 school year.

That trial lasted three months, in part because prosecutors introduced decades of church records to show how Lynn's handling of Avery's case was part of a long-standing practice of covering for and transferring deviate priests.

Lynn, 61, secretary for clergy from 1992 to 2004, was the archdiocesan official responsible for investigating allegations against priests and recommending action to the Philadelphia archbishop.

The forthcoming trial of ex-priest Charles Engelhardt, 65, and former parochial schoolteacher Bernard Shero, 49, should be shorter - possibly just two weeks - because it will focus only on what happened to Billy at St. Jerome's.

As with the earlier trial, trying to gauge what will happen is difficult because Judge M. Teresa Sarmina, who presided over Lynn's trial, has left in place the gag order prohibiting lawyers or witnesses from talking to reporters.

Even a hearing on pretrial motions Thursday was conducted in chambers. Documents relating to the hearing were sealed by the judge.

Tuesday's court session will begin with judge and lawyers - Assistant District Attorneys Evangelia Manos and Mark Cipolletti; Engelhardt's attorney Michael J. McGovern, and Shero attorney Burton A. Rose - selecting a jury of 12 and several alternates.

According to the 2011 grand jury report, Billy was first abused by Engelhardt after he served an early-morning weekday Mass with Engelhardt at St. Jerome's.

Engelhardt allegedly caught the boy in the church sacristy drinking leftover sacramental wine. Instead of scolding the boy, the priest allegedly poured him another, showed the boy pornographic magazines, and told Billy he would soon start sessions where the priest would teach him to "become a man."

About a week later, again in the sacristy, Engelhardt allegedly molested Billy and performed oral sex on the boy.

Two weeks later, Engelhardt again approached Billy, who rebuffed him, and Engelhardt then left him alone, the report reads.

A few months later, however, the report said Billy was approached by Avery, the chaplain at nearby Nazareth Hospital, who lived in the St. Jerome's rectory.

Avery had a history of sexually abusing children, and in 1992 Lynn ordered him to go to St. John Vianney, the archdiocesan hospital for priests with sexual or drug and alcohol problems. On his release, doctors recommended that Avery not serve anywhere where he could be in contact with children. Lynn assigned him to Nazareth, but then-Archbishop Cardinal Anthony J. Bevilacqua ordered that Avery be allowed to live in the St. Jerome's rectory.

The grand jury report alleges that Avery told Billy he had heard about the boy's "sessions" with Engelhardt. Avery allegedly performed oral sex on the boy and penetrated him with a finger.

They had another session several weeks later, the report reads, and Billy then avoided serving Mass with Avery.

After summer break, the boy returned to St. Jerome's for sixth grade and was assigned to Shero's classroom.

The grand jury report alleges that one day Shero offered Billy a ride home from school. Instead, Shero allegedly stopped the car and orally and anally raped the boy. He then told Billy to get out of the car and walk the rest of the way home.

For Billy, this trial will be a reprise of his appearance at Lynn's trial.

It's not known how judge and lawyers will deal with the legal issues raised by Avery. On March 22, on the eve of jury selection in the first trial, Avery pleaded guilty to sexually assaulting Billy in 1999 and was immediately sentenced to 21/2 to 5 years in prison.

Although Avery's plea agreement did not require him to testify at the forthcoming trial, the 69-year-old priest was suddenly transferred last week from the state prison at Laurel Highlands in Western Pennsylvania, where he was serving his sentence, to the state prison at Graterford in Montgomery County.

Cipolletti said he could not comment on the transfer because of Sarmina's gag order, and Avery's lawyer could not be reached for comment.

Lynn is serving his 3- to 6-year term in the state prison at Camp Hill near Harrisburg.

Engelhardt and Shero were originally charged with Lynn, Avery, and the Rev. James J. Brennan after the grand jury's 2011 report. Sarmina later agreed to sever their cases because neither was under the direct supervision of Lynn or other archdiocesan officials. Engelhardt was a priest in Philadelphia under the authority of an independent order, the Oblates of St. Francis de Sales.

Brennan, 49, will be retried March 6 in the alleged attempted rape of a 14-year-old boy in 1996. Brennan was tried with Lynn, but the jury was unable to reach a verdict in his case and a mistrial was declared.