Private police agencies offered employers the last form of union oppression. This form of industrial coercion proved to be clear by constitutional protection as the men employed by the corporations were not held accountable to anyone but their employers. Witnesses in industrial communities revealed to the committee the abusive power of private police; their constant harassment and use of physical violence repressed the First Amendment rights of citizens. Like espionage, munitions utilization, and strikebreaking, private police agencies testified to the incompatibility of industrial tyranny over the liberties of industrial workers.