and triggered a condition called anterograde memory loss, possibly the most serious way to impact anyone's ability to investigate anything.

Anterograde memory loss is a form of amnesia that prevents the formation of new memories, but doesn't break anything else in the brain. Therefore Shelby can remember his life before what is consistently referred to as 'the incident', right up to seeing his wife in the bathroom, but nothing further from then on except for the previous few minutes. But hey, he gets there in the end, right? After all, we see it at the beginning of the film. We see Shelby get his revenge by killing John G. Well it's not quite that simple. It's more than a little strange watching an investigation in reverse, scene by scene,gun and he forgets during the chase who's doing the chasing. So he defines a system, beginning with a tattoo on his left hand that reads 'Remember Sammy Jankis'.

Because he knew Jankis before the incident his memory of him isn't lost and he knows precisely what that tattoo is supposed to trigger: the recollection system. Sammy was a man he investigated who had the same condition and wrote things down on notes. As Shelby is dealing with more serious things, he goes a step beyond mere notes to keep polaroids in his pocket that identify people and places and key information like who to trust and what people's motivations are. His own driving purpose he has tattooed onto his chest in mirror writing and whenever he is sure