For all of us who adored Justine, who thoroughly seems a mild mannered, yet coward and a bit egocentric girl, there is "hope" at the end. Unlike Alexis she is somehow really pulled into the whole thing. She doesn't seem overly self-confident and beside all her obvious faults plays the role of a minor hero in this film. In a classic teenie slasher she would definitely come out alive - which she did, but... ya know.
Anyway, the scene after the end credits hints toward an outcome apart from the obvious. Mullet is arguably not done with his killing spree, since it's perfectly clear that the football coach might bitterly regret his shallow attitude towards sportsmanship. If he is killed as well it indicates that neither Justine nor Alexis were the only ones to blame. That might cause the police to investigate further on that subject and inevitably at least THINK about the case again. Ask the PE class and you'll find out that Marcus babbled about Mullet shortly before his demise.
Now rethink his murder - could wispy Alexis really lift that muscleman one metre without obvious resistance? Wouldn't his shorts leave marks on his genitals after he is pulled upwards at them? (Which, by the way, is a great manner to do that). Who could physically do that? And what about Mullet's grave? Is it empty now, or what? Well, until the police aren't lazy folks, they will go after another killer.
It's unclear if - and when - Justine will profit from that. I mean, there's no Gil Grissom in England, is he?
Well, at least she lost her virginity BEFORE going to prison...