ANSWER:
The newspaper man could be a viable suspect.
The blood id dried means that the dead man was killed long time back.
The milk was warm, means it was delivered recently – may be a few minutes ago.
But the newspaper found on the porch was of Monday, which means that the last tine newspaper man made delivery was on Monday.
Why didn’t he deliver on the next three days? (Probably) because he knew that the man is already dead.
That makes him guilty of at least hiding a crime if not himself committing it.
(The newspaper man may argue that he didn’t deliver the papers after Monday because the (now-dead) man had told him (on Monday) that he was going out of town for a week or so.
But the argument is weak, because, had the man planned any such trip, he would have informed the milkman also, and he also wouldn’t have made the delivery.)