Can a motion for a mistrial be denied because of the sudden availability of an expert witness?

also, People v. Dunn (2012) 205 Cal.App.4th 1086, 1100 [employing same rationale where basis for mistrial motion was the sudden unavailability of an expert witness].) We are not persuaded that the trial court's ruling was erroneous. In any event, the witness's improper testimony can only be viewed as harmless when considered in light of the overwhelming evidence of defendant's guilt. Therefore, the trial court did not commit reversible error by denying the motion for a mistrial.