Spangler, 39, is charged in connection with a March 19, 2008 blaze at a building where he was living next to the police station in downtown Big Sandy. It was at one time a feed store.
He has also been indicted on a separate charge of insurance fraud arising from the fire, but is being tried only on the arson charge next week.
The trial is expected to last through Wednesday, said Upshur County Assistant District Attorney Edward Choy. He said either District Attorney Billy Byrd or fellow Assistant District Attorney Christie Martin would join him in prosecuting the case.
Defense attorney Bobby Mims of Tyler told the jury panel in the case Tuesday that if Spangler is convicted, the jury would not determine the sentence.
That means 115th District Judge Lauren Parish, who is presiding in the trial, would assess sentence.