A Cook County judge ruled Tuesday to keep most of the police documents related to the 50 year old murder of Valerie Percy sealed.
Percy, the daughter of former Illinois Senator Chuck Percy, was beaten and stabbed in her Kenilworth bedroom in 1966.
In her ruling today, the judge said the case remains an active investigation, and therefore the documents should be sealed.
The release of any of the documents related the killing would "jeopardize the investigation" and "thwart the efforts" of authorities, Judge Demacopoulos said.
-The Chicago Tribune contributed to this report.