Rear Window Wiper Washer problems of the 1997 Cadillac Deville

I am the owner of a 1997 Cadillac Deville that has an on-going history of windshield wiper failure. The car has been looked at by my mechanic on numerous occasions for this problem between June 2007 and September 2008. On several occasions the wipers were inoperable when I arrived at the mechanic's facility. On the other occasions the wipers became operable by the time I arrived at the mechanic's facility. The Cadillac dealers display no degree of concern in dealing with this problem. In my opinion, all evidence points to a design or manufacturing defect, which could ultimately lead to a crash, or cause injury or death. I bring this matter to your attention because I have lost confidence in any repair recommendations. Further, I am concerned for my safety and the safety of others when I drive this vehicle during inclement weather. I fear the potential for expensive litigation that could follow an accident caused by this problem. I solicit your comments and/or recommendations. Stanley l fastenau.