While those of us at SpoilerTV were awfully sad to see Dewey Crowe finally meet his fate, the rationale provided by Graham Yost is hard to argue with:
"We felt like if Boyd was to kill someone who was pretty harmless -- hapless perhaps is a better word -- just on a suspicion, then what would he do if he found out that Ava was betraying him?"
Herriman himself had this to say over it:
TV Guide: When did you find out that Dewey was going to die?Read more on TVGuide to see what else Herriman had to say.
Damon Herriman: I was doing the DVD commentary with Graham and a couple of the other producers for Season 5 and they said, "Damon, there's something we need to tell you." At that point, I didn't know for sure if Dewey was even coming back in Season 6. They were like, "Yeah, Dewey's coming back... but it's good and bad news. He's back, but he's actually going to die." That was definitely a bit of a shock. It's kind of weird. It's like hearing that someone you know has passed away.
