Dave is an outgoing and rather unhinged man, showing no guilt for the crimes he committed. While he can be outwardly friendly to others, he's not afraid to kill them at a moments notice. This is due to Henry's tampering with his brain, messing his mind up to the point where he genuinely cannot feel empathy for the things he has done.

Dave seems to have an obsession with Jack (and also with the nickname "Old Sport") judging by how he tries to befriend and putting him in his scheme.