The historical evidence in question, sometimes called "other bad acts evidence," has been at the heart of Lynn's case since 2011, when he was charged with three priests and a parochial school teacher after a local grand jury probe.
Lynn, now 65, was not accused of molesting children. Instead, he was accused of child endangerment because, as the archdiocese's secretary for clergy from 1992 to 2004, he allegedly reassigned pedophile priests to new parishes, where they preyed on more children.
At the landmark 2012 trial where Lynn was found guilty, Philadelphia Common Pleas Court Judge M. Teresa Sarmina let prosecutors introduce documents from the archdiocese's "secret archives" about problem priests. She ruled that the background was needed to help the jury understand the context and culture in which Lynn made decisions about how to handle accused clergy.
Lynn's lawyers, however, called the evidence prejudicial, and said it inflamed the jury and impelled a guilty verdict.
Lynn was sentenced in July 2012 to three to six years in prison. He is being held at the state prison in Waymart, northeast of Scranton.
The prosecution's appeal argues that the jury could not have been swayed by the historical evidence because it could not reach a verdict against one Lynn codefendant, and because it acquitted Lynn of three charges.
The petition also cited the recent state grand jury report documenting child sex abuse by priests in the Catholic Diocese of Altoona-Johnstown.
"The revelations . . . show that this court's review is necessary to clarify what kind of evidence may be admitted in future cases of institutional concealment of child sexual abuse," the petition states.