Question: Why would Luke Dempsey be arrested along with his father? He had no idea what his father was doing, never aided him in any way and only found out the truth after catching him in the act.
Continuity mistake: The bullet hole in Davidson's chest is not at all where he was shot.
Phillip Broyles: Someone out there is experimenting, only the whole world is their lab.
More trivia for Fringe
Answer: He helped his father evade capture, impeding the investigation.