observer, bystander, onlooker, spectator, eyewitness, viewer, beholder, watcher, testifier, deponent, attester, perceiver, looker-on, witnesser, seer
defensible - legitimate - reasonable - warranted - acceptable - permissible - excusable - valid - supportable - tenable - sustainable - allowable - understandable - explainable - rational - fair - right - proper - fitting - appropriate - suitable - just - lawful - authorized - sanctioned - vindicable - arguable - plausible - credible - sound - logical - cogent - well-founded - well-grounded - justifiable
Justifiable refers to something that can be shown to be reasonable or warranted under the circumstances. In legal terms, it implies that an action, decision, or claim can be defended as valid and appropriate given the context in which it was made. It often relates to actions that are in accordance with justice, ethics, and principles.