"Penal Code section 1127c requires that whenever evidence of flight is relied on to show guilt, the court must instruct the jury that while flight is not sufficient to establish guilt, it is a fact which, if proved, the jury may consider." (People v. Pensinger (1991) 52 Cal.3d 1210, 1243.) An instruction on flight is appropriate if there is substantial evidence the defendant departed the crime scene under circumstances suggesting the movement was motivated by a consciousness of guilt. (People v. Howard (2008) 42 Cal.4th 1000, 1020.) "Flight requires '"a purpose to avoid being observed or arrested."' " (People v. Avila (2009) 46 Cal.4th 680, 710.)