Cylinder Gas, Chemical, Petroleum, Auto-Service & Accessory Drivers, Local No. 283 v. Ottawa Silica Co.

How later courts describe this case

• prosecutorial immunity not available when a civil rights claim "focuses on a prosecutor's actions in the course of directing police investigative activity”
• attempted suit against Mayor and Police Superintendent on theory that they knew of a conspiracy by their subordinates against the plaintiffs
• "the State's Attorney's alleged participation in the planning and execution of a raid of this character has no greater claim to complete immunity than activities of police officers allegedly acting under his direction"
• availability of immunity depends on character of conduct under attack
• nature of prosecutor's immunity depends upon character of conduct
• use is bar where not purely experimental
• Justice Stevens, then circuit judge