MACKELL IS GUILTY ALONG WITH AIDES IN QUEENS SWINDLE
Thomas J Mackell, James D Robertson and Frank DePaola convicted of official misconduct and conspiracy on Mar 2, in blocking prosecution of Joseph Ferdinando, perpetrator of fast-money scheme; Mackell is 1st NYC Dist Atty in city's history to be indicted, tried and convicted on state charges for crimes committed while in office; defendants face up to 1 yr in jail on each of 4 misconduct counts and 3 mos for each of 2 conspiracy counts, and up to $5,000 fine; Mackell plans appeal; special prosecutor Nadjari comments; case detailed; illus (L)
