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* Ok, even accepting the premise as a whole, why does Shepherd in the future look the same in the final scene as he did the first time John met him? They'd changed the timeline so that he had to fake his death and go on the lam 30 years earlier. He shouldn't be clean-shaven, and wearing a nice suit. He probably just spent 30 years in the criminal underworld.
** It's entirely possible for someone to hide in plain sight, with a respectable job which involves wearing a suit (they said he'd been a private detective after leaving the police force, so it could be that). Faking his death means the police wouldn't be looking anyway.
** Or he got caught, was sent to prison, got paroled and stole a gun to take revenge on John. The only way for his faked death to work (it was blown the moment he attacked them in 1969) is if Frank, Julia and John didn't say a word and cleaned up the mess he made in their house.
** Or he really did go into hiding and got work through his criminal connections. His father had mentioned that he got caught up in the Knapp hearings. Maybe in his act of revenge, he decided to clean up and dress in a suit for the occasion.
* Why didn't John and Frank just use the fingerprints on the wallet as evidence in 1969, instead of leaving it for John in 1999?
** Because the night John and Frank came up with the plan, they didn't even know who Jack was, much less have any evidence to connect him to the Nightingale murders. Confirming his identity took priority.
** As evidence, all it would have shown was that Jack touched Frank's wallet at some point - and wouldn't have helped at all when Frank's ID was found under the victim and a witness saw him there. It also wouldn't have helped much after Jack attacked the Sullivans, as at most all it does is place him at the bar that night. But by that point the cops already have his mementos as evidence, and probably some eyewitness accounts as well. (The two hippies would serve as better evidence anyway, because they could actually place Jack and Frank at the bar.)
** It's an example of TechnologyMarchesOn: Because doing the investigative leg work in 1969 would have required hours if not days of intensively poring over paperwork, which is time the two didn't have, while in the futuristic world of 1999, John could just get his police friends to run it through a computer for a DNA search. Also because John, in 1999, is the cop, not Frank.

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