Keith Kalota was found not guilty by reason of mental disease after stabbing his wife, Debra, his 4-year-old daughter, Constance, and 2-year-old son, Jacob, at their Milwaukee home in 1987.
Kalota spent 16 years at the Mendota Mental Health Institute in Madison before he was released.
Kalota was among 28 potential jurors questioned for a firearm silencer possession trial this week.
Kalota said he had been told he could serve as a juror because he was never convicted of a felony.
The Journal Sentinel reports the defense attorney and the prosecutor asked that Kalota be eliminated as a potential juror.