How do courts review a motion to dismiss for prejudicial prearrest delay?

We review for abuse of discretion a trial court's ruling on a motion to dismiss for prejudicial prearrest delay. We defer to any underlying factual findings if substantial evidence supports them. (People v. Cowan (2010) 50 Cal.4th 401, 430 (Cowan).) Whether preaccusation delay is unreasonable and prejudicial to a defendant is a question of fact. (People v. Mirenda (2009) 174 Cal.App.4th 1313, 1330.)