The head of the grand jury that examined Sen. Edward M. Kennedy's role in the death of Mary Jo Kopechne says the panel never got a chance to properly investigate the fatal accident because of a political "cover-up," Newsweek reported. The Massachusetts Democrat received a suspended sentence for leaving the scene of an accident, but the grand jury never pursued felony charges, said Leslie Leland, foreman of the Dukes County grand jury. Kennedy could not immediately be reached for comment. Kopechne, a passenger, was killed July 18, 1969, when the car Kennedy was driving across the bridge at Chappaquiddick on Martha's Vineyard, Mass., skidded into the water. Leland said the grand jury was prevented from subpoenaing witnesses or examining a copy of the inquest.