What incredible chutzpah!!  In a transparent attempt to justify their blatant and despicable lying in covering up clergy sex abuse, Irish church leaders--following the bad example of  certain episcopal liars in the United States--have trotted out the controversial moral theological concept of "mental reservation" (see news story about Cardinal Desmond Connell, retired archbishop of Dublin here ).

Over the centuries, Catholic theologians have taken different positions on the justifiability of  “mental reservations.” And paragraph 2483 of the catechism went through an interesting revision around this centuries-old debate (see page 2 of this paper ).

But what that concept was intended to deal with was life-and-death situations or other grave injustices where telling the truth would endanger the life of somebody you are hiding or lead to some other awful consequence. The most commonly cited example goes something like this: If you lived in Nazi-era Germany, and the Gestapo knocked on your door asking you whether you were hiding any Jews in your home, and you were actually hiding a Jewish family, wouldn't a deceptive answer be justified?"

In any case, mental reservation is not about conveniently lying to save your sorry butt and could in no moral universe be justified to enable or cover up the horrendous crime of sexual abuse of children. As the old Catholic Encyclopedia entry aptly summarizes it: “A sin is committed if mental reservations are used without just cause, or in cases when the questioner has a right to the naked truth.”

For a good explanation of "mental reservation" and its inapplicability to the bishops' lying about clergy sex abuse, see also Father Tom Doyle's explanation:
"Under the present circumstances some claim that it is morally justifiable to lie in order to protect the reputation of the institutional Church. The lie generally is formulated in either an active form such as denying that a person has sexually abused children, or in a passive form, such as failing to inform a pastor or a parish that an assigned priest or cleric is a known abuser. In either case and under any guise [this scenario] never fulfills even the most remote circumstances for applying mental reservation. The concept of the 'good of the Church' never allows for enabling sexual abuse or covering for sexual abuse since the 'church' is hardly limited to the clerics or the hierarchy but includes the abused and the lay faithful susceptible to abuse."