Alice punches Bob. Or stabs him. Either way it was from behind and he did not see who did it before going unconscious, but the entire thing was witnessed by Charles. However there was no other evidence of Alice’s crime like video footage or the like.
Charles testifies as to what he witnessed. Is Charles’s word enough to convict Alice of a crime?
What if it was also witnessed by Diana and they both testify, what then?
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Or, Generally speaking, if someone presents to police and then court saying with a consistent narrative of events “this person hit me at the place and this time,” and there is perhaps a bruise to back it then that is often enough to convict the accused?