GRAY IS REPORTED WILLING TO WAIVE TRIAL IMMUNITY
Former FBI acting dir L P Gray agrees to testify without immunity in any Watergate criminal trials about his dealings with Pres Nixon and other top Adm officials after Watergate break-in; Gray reptdly decided to testify without immunity in hope he would not be indicted as result of any high-level attempts to cover up Watergate affair; Govt source confirms Gray has been cooperating for last mo, but refuses to say whether criminal charges will be filed against him; Gray is considered key witness for Fed prosecutors, as is H W Kalmbach, formerly Pres Nixon's personal atty, and J S Magruder, former Repub re-elect campaign official; both Fed prosecutors and officials close to special Watergate prosecutor A Cox are known to believe that naivete and eagerness to please led Gray to become 'a victim' of sr White House aides, and as such, less culpable than those aides who actually directed cover-up