Faster/Headscratchers

Spoilers Ahoy!

Why didn't Cop just let Killer shoot Driver?
Killer does what he was hired to do, Cop swoops in and caps Killer. He's in the clear¹. Why implicate himself by shooting Driver himself? Or at the very least, why not shoot them both?


 * 1) We know Cicero put it together, but he didn't know that. And it's not like she had any hard proof anyway.
 * 2) Also Killer isn't working directly for Cop, but through a third party, presumably organised crime who might cause trouble for Cop if their best hitman was killed by a client. Furthermore Killer's body would still raise questions as to who he was -- Cop shooting Driver, even in the back of the head ("I saw him reach down to pick up the gun! I feared for my life!") would wrap everything up neatly.

Driver's prison sentence
Ten years for a bank robbery with no fatalities or collateral damage? AND after he'd been shot and left for dead? Really?
 * Well, he wasn't getting any time taken off for good behavior. He was a mule, smuggling items in and out, and while he didn't start any fights, he absolutely brutalized people who started fights with him(and prisons rarely give a shit who starts it), so he probably got time added on.

Driver's tattoo
We're never told what the thing actually means or where he got it, only that it has something to do with ghosts and it was enough to chase off a 300lb Samoan. You can't set up that kind of badass cred then just ignore it!
 * There probably WAS a scene that explained the tattoo and it ended up getting cut from the film.
 * It looked like a fairly unique tattoo, maybe something he got while in prison. I got the impression that the Samoan called Driver a ghost for surviving a point blank bullet shot to the head and living to tell about it. If someone told me to fight a man who survived something like that, I'd probably back away, too.
 * It gets mentioned off handedly when Cicero and Cop identify him; Cop mentions he "kept score". It's a trophy list keeping track of his altercations in prison. He survived ten years without gang protection without ever backing down from a fight and absolutely brutalizing those who started shit with him.
 * The tattoo and the "Ghost" appellation probably has some cultural significance to native Samoans, now imagine what would happen to that significance if it was ever fully explained within earshot of any suburban white kids.

=== Given that Driver never tries to conceal his face or his Cool Car, how come the Highway Patrol doesn't intercept him halfway through the movie? ===