i listened to the final episode this afternoon.
Just gotta say he is a poor presenter, a poor investigator, and seems to hate the Police.
Dunno whether it is a coincidence but a lot of the people he spoke to either had a criminal past, or hated the Police.
Also, it seems the Police did speake to many people in Whangamata including the guy Turner. they would have heard most of what Wolf found,
I repeat my earlier guess, is that the murders were the result of a drug deal gone wrong, the Police could not find enough evidence to charge anybody, because they were all a bunch liars, so they were sparing the family, and the memory of the poor victims the bad publicity.
Oh, and Tamihere killed Heidi, dunno about Sven though.
Just IMO