INDIANAPOLIS (AP) _ Three people charged with deliberately triggering a house explosion that devastated an Indianapolis neighborhood and killed two people are set to appear in court for a pre-trial conference.
 
  Prosecutors and lawyers for Mark Leonard, his girlfriend, Monserrate Shirley, and his brother Bob Leonard are expected to debate numerous motions at the pre-trial conference Wednesday afternoon in a Marion County courtroom.
 
  The three are charged with murder and arson in the Nov. 10 explosion. Teacher Jennifer Longworth and her husband, John, were killed in the blast that also left 33 homes so damaged they had to be demolished.
 
  Investigators believe Mark Leonard and the others conspired to fill the house up with natural gas, then set a microwave to start on a timer, sparking the blast.