adviser announcer annunciator attestant attestator attester authority bystander channel cojuror communicant communicator compurgator deponent earwitness enlightener examinant examinate examinee expert witness eyewitness gossipmonger grapevine information center information medium informer interviewee monitor mouthpiece newsmonger notifier passerby press public relations officer publisher questionee quizzee radio reporter source spectator spokesman subject swearer television teller testifier tipster tout voucher witness