Juries in criminal trials do not base verdicts on uncorroborated testimony given by any one witness  Rightly so, because it is usually prudent to be highly skeptical of unsubstantiated claims made by any one person
But then, to be consistent, juries should end an all-too-common practice: convicting defendants on the basis of an uncorroborated full confession
The process of jury selection is designed to screen out people who have a firm opinion about the defendant's guilt in advance of the trial.