After helping his wife into their car, Calvin Walker walks past a message on his rear windshield and the media who had surrounded him and his wife after leaving the Federal Courthouse Thursday afternoon.  U.S. District Judge Ron Clark declared a mistrial in the Calvin Walker federal trial. The 12 person federal jury was deadlocked on reaching a verdict in the case.  Walker, 51, right, the Beaumont Independent School District's electrician of record, was accused of defrauding and overbilling the district by nearly $4 million. He was indicted on 37 federal counts in May. Dave Ryan/The Enterprise