With a fine series like Broadchurch, you can usually tell who the killer is not by discounting who the killer most likely appears to be in the early episodes. Here's where we stand as of episode 1.4 as far as likely killers who likely not to be revealed as the killer at the end:
The old guy who may have some history as a pedophile: His denial seems sincere, and he's in any case too obvious a suspect at this point.The unpleasant woman who had some of Danny's stuff in her closet, and most recently threatened the editor of the local paper: She's a despicable piece of work, to be sure, and she may turn out in the end to have helped the killer, or know who the killer is, but she's just as likely to be killed by the killer because of her nasty attitude.The priest is just too obvious: The show is spending a good deal of time on him, but the priest as killer is just too trite for a story like this.So where does that leave us? Someone in Danny's family is still a possibility, including the father who now seems exonerated. Danny's sister seems an outside shot. I'd say Danny's mother and grandmother are beyond the pale as possible suspects.
How about Ellie's family? Her son obviously knows stuff he's not talking about, but he's not the killer. There's something about Ellie's husband that makes me wonder about him - he's, I don't know, maybe too nice? We have no reason at all to suspect him as the killer, which puts him higher on the list than those we have ample reason to suspect.
But if I had to pick someone now, I would say it was Danny's father's partner. Another nice guy who seems to want to do nothing more than be of help, but there's an edge to him. So I'd put my money on him at this juncture.
More after the next showing.