Aggressive police questioning of a weak-willed suspect can produce an occasional false confession, but experts now believe that six men in a single case, and four in another, confessed to group crimes they did not commit, even though some described their roles in vivid detail. Recent DNA evidence in a 1989 Beatrice, Neb., murder case implicated only a seventh man, and similar evidence in a 1997 Norfolk, Va., murder case implicated only a fifth man, who insists he acted alone.
