In their 29-page brief, the prosecutors told the judge only the stiffest term would send a message to Lynn and other church leaders.
"A maximum sentence," they wrote, "may be the only way to impress upon the defendant that he committed a serious crime, that there are more important rules to follow than instructions from corrupt or misguided bishops, and that the protection of children trumps the reputation of abusers and the institution that harbors them."
Lynn's lawyers say such a harsh term would be unfair and legally flawed.
In their filing to the judge, they noted that the jury convicted Lynn of a single count - child endangerment - for not removing a former parish priest, Edward Avery, from active ministry in the 1990s after learning Avery had molested a teen.
In 1999, Avery sexually assaulted a 10-year-old altar boy at a Northeast Philadelphia church. That victim was one of nearly 20 to testify at Lynn's three-month landmark trial.
Lynn's lawyers say he had no reason to suspect Avery would abuse the boy. They also said he followed the recommendations of hospital psychologists when he agreed to let Avery live at the St. Jerome rectory and celebrate Mass at the parish.
They also noted that two-thirds of the defendants convicted of a third-degree endangerment felony in Pennsylvania since 1996 - as Lynn was - have been spared state prison terms.
The lawyers submitted several hundred letters of support for Lynn, a priest for 36 years who has no previous convictions.
Under their calculations of state guidelines, Lynn deserves probation or a county jail term of a year or less.
Prosecutors scoffed at the argument. They maintained that Lynn has a well-documented criminal history - one that unfolded during weeks of often gut-wrenching trial testimony from witnesses who described being fondled, molested, or raped by their parish priests.
As the archdiocesan secretary for clergy responsible for investigating the claims, Lynn saw the impact of the abuse but did nothing, Blessington and Sorensen wrote.
"He observed firsthand, on a regular basis the destruction of lives as victims of priests whom he supervised poured out their stories of abuse, shame, despair, isolation, anger, loss of faith, addictions, failed marriage, and lost lives," their motion stated.
Lynn's actions, they said, also had a devastating affect on Catholics in the area, causing many to question their faith and leaders, and costing the church millions of dollars at a time when financial woes are forcing parishes and schools to close.
"Given all that, the prosecutors argued, "his offense could not be graver. It easily merits the maximum sentence."
Contact John P. Martin at 215-854-4774, firstname.lastname@example.org, or follow @JPMartinInky on Twitter.