It's genius! If Tripp has no coffee,then he will be unable to concentrate, and therefore be unable to stop the Narvan's invasion! That or the assassin has terrible aim and luck worse than Tripp's.
This is why you test something before using it in a situation where having it not work would be bad. Well, that and he probably just needs to play more videogames.
Tripp? Look normal? That... actually doesn't sound to hard, but then why do I have this feeling that it will all go horribly wrong at the worst possible moment?