Witness Immunity for Evidence Not Actions

Docker and others v Chief Constable of West Midlands Police (TLR 1 August H of L)

The rule that a party or witness has immunity in respect of what he said or did in court had been established for centuries. The reason for it was grounded in public policy: it was to protect witnesses from being harassed and vexed by actions for defamation in respect of what they had said.