A late chief justice, William Rehnquist, hallucinated about being the victim of a CIA plot while struggling to break a decade-long dependence on a prescription sedative, according to newly released FBI files.

Rehnquist’s use of large doses of the medication, Placidyl, became public in 1981 when he was hospitalized for back pain and drug-related complications. The issue arose again in 1986 when he was nominated as chief justice, but it did not impede his confirmation.

Much of the information disclosed last week under the Freedom of Information Act comes from an FBI investigation conducted in connection with Rehnquist’s 1986 nomination. Part of the inquiry sought to determine how the jurist obtained about 1500 milligrams of the drug each day when the recommended maximum dose was 500 milligrams.

A Washington newspaper that requested the file, Legal Times, reported that one doctor interviewed by the FBI said Rehnquist was so disoriented during his hospitalization that he went “to the lobby in his pajamas in order to try to escape.”

Prior to the 1981 treatment, the justice sometimes slurred his speech, court observers said, but no evidence indicated that his work was affected.

The files also describe the FBI’s efforts in 1971 to support Rehnquist’s nomination as an associate justice. The bureau conducted background checks on two Phoenix, Ariz., residents expected to testify against Rehnquist, Legal Times said.

The files also detail a scandal surrounding the FBI’s interviews of other potential Rehnquist critics, including a Harvard Law School professor, Laurence Tribe.

Rehnquist died in 2005, at age 80.