By Tony Hanson

PHILADELPHIA (CBS) — The prosecution in the clergy abuse case presented disturbing evidence Wednesday as it tries to make its case that defendant Monsignor William Lynn was part of a decades long conspiracy to protect predator priests while endangering children.

The priests from these old cases have not been charged.

A man testified he was targeted on the street. A priest in civilian clothes spotted him buying pornography as a teen in 1991, noted his Bishop Neumann High School jacket, and then tracked him down to the school, pulled him from class and then molested him.

Authorities say the priest had been the target of previous complaint.

The jury heard a vile letter allegedly written by a priest in 1995 to a 7th grade boy in his parish, soliciting sex. But the letter was intercepted and sadomasochistic pornography was found. Father Michael Murtha was treated at the Archdiocese hospital, but remained in active ministry for over a decade.