Can a motion for a mistrial be made against a witness in a criminal case?

Sloan contends the court erred by denying the motion for a mistrial. " 'A mistrial should be granted if the court is apprised of prejudice that it judges incurable by admonition or instruction. [Citation.] Whether a particular incident is incurably prejudicial is by its nature a speculative matter, and the trial court is vested with considerable discretion in ruling on mistrial motions.' [Citation.] Although most cases involve prosecutorial or juror misconduct as the basis for the motion, a witness's volunteered statement can also provide the basis for a finding of incurable prejudice." (People v. Wharton (1991) 53 Cal.3d 522, 565.)