The judge in the Christopher Vaughn quadruple murder case will decide later this month whether to bar testimony from an expert defense witness or to hold a hearing to determine the expert's reliability.

Will County Judge Daniel Rozak set June 18 as the date to settle the matter during a brief court hearing Friday morning.

Vaughn, 37, has been jailed since June 2007 on charges he murdered his wife, 34-year-old Kimberly Vaughn, and three children—Blake, 8, Cassandra, 11, and Abigayle, 12.

On the morning of the killings, the Vaughn family was heading from their home in Oswego to a Springfield waterpark when Christopher Vaughn pulled off Interstate 55 and stopped on the frontage road outside Channahon and near Shorewood.

It was there Christopher Vaughn murdered his wife and children as they sat in the family's minivan, according to police and prosecutors.

Vaughn told detectives it was actually his wife who shot down their children, put a bullet in his leg as he fled for his life, then turned the gun on herself and committed suicide.

Christopher Vaughn reportedly explained to detectives that he had confessed to his wife about an extramarital dalliance, and that was what led to the unhinged Kimberly Vaughn's killing spree. Medication for migraine headaches also contributed to her becoming both homicidal and suicidal, officials said Christopher Vaughn told detectives.