What is the test for 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 [citation], and defer to any underlying factual findings if substantial evidence supports them [citation]." (People v. Cowan (2010) 50 Cal.4th 401, 431.) Finally, "[t]he determination of whether a continuance should be granted rests within the sound discretion of the trial court." (People v. Sakarias (2000) 22 Cal.4th 596, 646.) Absent a showing of abuse of discretion and prejudice to the defendant, the denial of a motion for a continuance does not require reversal of the judgment. (People v. Samayoa (1997) 15 Cal.4th 795, 840.)