Haloperidol is not a sleeping pill as stated in the show. Haloperidol is used to treat psychotic disorders. Haloperidol is in a group of medications called conventional anti-psychotics. It works by decreasing abnormal excitement in the brain.
Barnaby, then later Troy identify the Black Saab as a 900, it was a 9000.
When Troy lifts Alan Hollingsworth's eyelid to see if he is dead his left eye partly opens, this would not happen if he were dead.
When Barnaby is inspecting the CD player at the Buckley's house, he clearly chooses 'Down to the Doctors' by Dr Feelgood, a British R&B band.
However when the music starts to play it is a light orchestral piece.