(n.) One who sees a thing done; one who has ocular view of anything.

TV-viewer absolute adducible admissible attestant attestative attestator attester attestive authentic based on beholder bird-watcher bystander certain circumstantial cojuror compurgator conclusive convincing cumulative damning decisive deponent determinative documentary documented drugstore cowboy earwitness evidential evidentiary ex parte eye-witness factual final firsthand founded on gaper gazer gazer-on girl-watcher goggler grounded on hearsay implicit incontrovertible indicative indisputable informant informer irrefutable irresistible kibitzer looker looker-on material nuncupative observer ogler onlooker overwhelming passerby perceiver percipient presumptive probative reliable seer sidewalk superintendent significant spectator spectatress spectatrix suggestive sure swearer symptomatic televiewer television-viewer telling testifier valid video-gazer viewer voucher watcher weighty witness