PHILADELPHIA (AP) — Jury selection began Monday in the trial of a Roman Catholic priest and a former Catholic school teacher charged with sexually assaulting a former altar boy.

Four jurors were chosen on the first day of jury selection in the case against the Rev. Charles Engelhardt and Bernard Shero. The case had been spun off from last year's high-profile trial of a church official charged with helping the Philadelphia Archdiocese cover up abuse complaints.

Engelhardt, 65, and Shero, 49, have pleaded not guilty to sexually assaulting the boy in the late 1990s.

Their accuser is a troubled 23-year-old policeman's son. He has a long history of drug addiction and arrests for drugs and petty crimes, and his credibility is expected to be the key trial issue.

He told a grand jury that he was passed around by three predators, starting when he was 10 years old, at St. Jerome's parish in northeast Philadelphia.

The young man said now-defrocked priest Edward Avery sexually assaulted him after Mass. He said Engelhardt assaulted him after catching him drinking wine in the sacristy and Shero, his sixth-grade teacher, attacked him after offering him a ride home.

Avery is serving 2½ to five years in prison after admitting he assaulted the boy. Engelhardt and Shero face much longer terms if convicted at trial. A gag order prevents lawyers from commenting on the case.

Lawyers representing Engelhardt and Shero wanted them tried separately from the defendants in last year's case. The Rev. William Lynn, 62, is appealing his conviction in that landmark case, while serving a three- to six-year prison term. Lynn was the first U.S. church supervisor convicted of endangering children by helping the church shuttle accused priests from parish to parish.