Chester Weger died last year at the age of 86. He was paroled in 2020.
Weger was convicted in 1961 for killing Lillian Oetting. He was also accused of the beating deaths of Mildred Lindquist and Frances Murphy at Starved Rock State Park.
Weger always maintained that he was innocent.
He spent 60 years behind bars.
"Chester was humble, generous and kind. The injustice he suffered during his lifetime is unimaginable. Rest assured, we will continue our efforts to obtain the justice that Chester so deserves," attorney Andy Hale previously said.