If he knows anything and he knows he's in trouble for it he probably doesn't care. She's dead what's he gonna do about it? If he doesn't know anything then they have probably already determined that. It's also possible his lawyer is just being smart and it has nothing to do with his knowledge of the crime. JMO
Hearing about the Oxy dealing makes the story of Hayleigh accidentally overdosing on Oxy very believable.
Well, it was clear that these folks were deep into the drug culture before the arrests anyway, so the arrests should really affect anyone's view of possible scenarios regarding Haleigh.