Chris Coleman, 34, allegedly committed the triple homicide because he wanted to marry a woman he was having an affair with, the Belleville News-Democrat reported. If he had gotten a divorce, he would have lost his job with Meyer.
Prosecutors and defense attorneys gave brief opening statements before testimony began.
The first witness, Columbia Police Sgt. Jason Donjon, described finding the bodies of Sheri Coleman and the boys May 5, 2009. Jurors were shown graphic photos of the bodies and the crime scene.
Police also found the words "I am always watching" and "Punished" spray-painted on the walls. Prosecutors say Coleman spent months sending threatening e-mails from his own laptop that purported to come from a group trying to close down Joyce Meyer Ministries.
The trial did not attract the huge crowds officials had prepared for, the News-Democrat said. The 20 spectators were outnumbered by reporters and camera crews, most of them from St. Louis.
Jurors were bussed in from outside Monroe County because of pretrial publicity.