Vaughn's trial is scheduled to start August 13. It could last for two months.
Kimberly Vaughn and the couple's children, aged 12, 11 and 8, were found shot to death in an SUV near Interstate 55 just outside of Channahon in June 2007.
Court records show the children were each shot twice and Kimberly Vaughn was shot once.
Christopher Vaughn was also shot. Defense attorneys have argued that his wife shot him and the children before turning the gun on herself.