Sarmina first ruled Bevilacqua legally competent in late November after a two-day private hearing at which the cardinal, who retired in 2003, was questioned by the judge, Bergstrom, and a prosecutor. Bergstrom subsequently renewed his motion to disqualify Bevilacqua from testifying.
Sarmina said she might revisit the competency issue if prosecutors decide to call Bevilacqua to the witness stand.
Jury selection in what is expected to be a months-long trial begins Feb. 22, with testimony to start March 26.
Lynn, 61, was secretary for clergy for 12 years under Bevilacqua, beginning in 1992. As such, he was responsible for pastoral assignments and disciplinary actions against priests.
Prosecutors have argued that Lynn's decisions involving pedophile priests were part of a long-standing practice in the Archdiocese of Philadelphia of transferring deviant priests to new, unsuspecting parishes.
Lynn's attorneys have said Bevilacqua should be ruled incompetent to testify because his mental deterioration has made it impossible for them to cross-examine the prelate to rebut the prosecution.
"He could not even identify my own client," Bergstrom argued, adding: "He didn't remember about a 20-year time period."
With the judge's permission, Bergstrom and a prosecutor questioned Bevilacqua for two days in November to gauge how age and illness have affected his memory and ability to communicate.
Bevilacqua, for example, has no memory of his 10 appearances in 2003 and 2004 when he was called to testify to the first county grand jury that investigated clergy sex abuse, Bergstrom said.
Assistant District Attorney Patrick Blessington argued Monday that Bevilacqua's memory problems would be no more problematic for a jury than a hostile witness who refuses to submit to defense questioning.
In other developments, Sarmina promised to rule by Monday on whether prosecutors may introduce evidence at trial about other incidents of priests in the archdiocese sexually abusing altar boys and other children.
Prosecutors insist such evidence is necessary to help the jury understand how pedophile priests were able to prey on their young parishioners and, after being exposed, get transferred to new parishes to repeat the conduct.
Defense attorneys argued that such evidence is not relevant to the charges against Lynn and the three priests. The evidence would only inflame and prejudice the jury against the defendants and ensure guilty verdicts, defense attorneys said.
Contact staff writer Joseph A. Slobodzian at 215-854-2985, firstname.lastname@example.org, or @joeslobo on Twitter.