depends on whether its just a county sherriff or GSP.

county sheriff - keep going. he probably wont even think about putting his car in drive anyway. he'll just wait for the next person driving 15 over & give THEM a ticket.

gsp - pull over the second i spot him. no matter if he pulls out, puts his lights on or what. gsp will chase you until you either pull over or you get into a wreck & kill yourself.