US Catholic clergyman Monsignor William Lynn has been sentenced to three to six years in jail for covering up child sex abuse by priests in Philadelphia.

Lynn is the most senior U.S. cleric convicted in the church’s decades-long sex abuse scandal.

NBC reports that the sentence which was handed down by Judge M. Teresa Sarmina was less than the maximum penalty of seven years in prison for Lynn’s conviction on a single count of child endangerment.

The judge said: “The sentence is meant to punish Lynn for protecting monsters in clerical garb who molested children … to destroy the souls of children, to whom you turned a hard heart.”

She added: “You knew full well what was right, Monsignor Lynn, but you chose wrong.”

Lynn, now 61, acted as secretary for the clergy for the Philadelphia Archdiocese from 1992 to 2004 when he was in charge of 800 priests.

He was convicted last month of covering up the allegations by transferring predatory priests to unsuspecting parishes.

Lynn was acquitted of conspiracy and a second endangerment count.

Reports say the jury deadlocked on a 1996 abuse charge against a co-defendant, the Rev. James Brennan, who will now face a re-trial.

Commentator Terence McKiernan, president of BishopAccountability.org, which tracks priest-abuse cases, told NBCPhiladelphia.com: “I believe that what Lynn did was done by just about every diocese.

“In most cases, I think the vicar general was well informed, and also the bishop.”

“More than 500 U.S. priests have now been convicted of abuse but Lynn’s three-month trial shows just how hard it is to demonstrate collusion.”

Lynn has been in prison since the June 22 jury verdict when the trial judge revoked his bail.

Defense lawyers called Lynn a scapegoat for the Philadelphia archdiocese, and said they plan to appeal.

They will also ask that Lynn be released while the lengthy appeals process plays out according to NBCPhiladelphia.com.

His lawyers said the trial was flawed on many levels, starting with the fact that Lynn was charged with child endangerment under a law revised in 2007 to include those who supervise the caretakers of children.

They say that Lynn had left the archdiocese headquarters in 2004, after serving 12 years as secretary for clergy, and returned to parish work.

Prosecutors pushed for the maximum seven-year sentence, NBCPhiladelphia.com reported.

They claimed: “His active, even eager execution of archdiocese policies, carried out in the face of victims’ vivid suffering, and employing constant deceit, required a more amoral character, a striving to please his bosses no matter how sinister the business.

“At any time during those 12 years, he could have had a moment of conscience.”

The report also states that Bishop Robert Finn and the Kansas City diocese face a misdemeanor charge of failing to report suspected child sexual abuse.

Both Finn and the diocese have pleaded not guilty, and are set to go on trial next month.