Christopher Vaughn is charged with murdering Kimberly and their three children.
Defense attorneys say Kimberly Vaughn fired the fatal shots before taking her life.
Day two of the Christopher Vaughn trial wrapped up early Tuesday. Attorneys for both sides left the courthouse without speaking publicly about the case.
Among those taking the stand for the prosecution today were Vaughn's father-in-law and sisters-in-law.
During questioning, assistant state's attorney Debbie Mills appeared to be trying to establish that Vaughn's wife, Kimberly, was happy and making plans for the future in the days and weeks before the shootings and would not have shot Christopher, killed her children and then herself, as defense attorneys contend.
Vaughn, is charged with killing his family inside their vehicle on Frontage Road just off of I-55 near Channahon in the early morning hours of June 14, 2007 as the family drove to a water park in Springfield. In court, Vaughn once again sat nearly expressionless during testimony.
The most emotional part of the day came when Kimberly Vaughn's sister, Nikki Isemann took the stand. "She was my best friend and baby sister," sobbed Isemann who had a hard time keeping herself composed.
Also testifying were the Vaughns' next door neighbors and friends Todd and Hillary Andrlik. The couple had dinner at the Vaughns' Oswego home the night before the shootings. "Kim appeared the way she always appeared, very friendly and talkative and inquisitive ... nothing out of the ordinary," said Todd Andrlick. However, on cross-examination, when asked about Christopher Vaughn's relationship with his children, defense attorney George Leonard asked "would you say that Chris was very protective of his children?" "Yes," answered Andrlik.
The state is expected to call several first responders from Channahon on Wednesday as well as a passing motorist who first came across Christopher Vaughn after the shooting.