What is the test for a motion for a mistrial in a criminal case where a defendant has admitted to a prior criminal record?

"[E]xposing a jury to a defendant's prior criminality presents the possibility of prejudicing a defendant's case and rendering suspect the outcome of the trial. [Citations.] [] Whether in a given case the erroneous admission of such evidence warrants granting a mistrial or whether the error can be cured by striking the testimony and admonishing the jury rests in the sound discretion of the trial court. [Citation.] '"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.]'" (People v. Harris (1994) 22 Cal.App.4th 1575, 1580-1581.)