"Mental Reservation" in Court

It appears that Archbishop Levada will be asked at his deposition whether the doctrine of "mental reservation" allows a Catholic to lie under oath.  From what I can tell (and I'm no expert), the Church teaches that lying is always wrong, but in limited circumstances the requirements of justice trump the requirements of veracity.  Can the requirements of justice ever trump the obligation of truth-telling in court?  If not, is it only because an oath was taken, or because the law's expectation of truth-telling enhances the ordinary obligation of truth-telling?

(HT: Open Book)

Rob