The GM has final say on who gets drafted, and may or may not take the advice of his Director of Amateur Scouting.
I believe it is fairly well documented on this board by insiders that that was indeed the case with Fischer.
Timmins and Gainey took the advice of a scout who was completely convinced that Fischer was the right pick for Montreal. This was despite Fischer having a terrible combine and a weak interview process. That scout no longer works for Montreal.
Sometimes the advice of a scout can lead to getting Jaroslav Halak or Mark Streit. Other times you draft David Fischer.
You can gauge your head of Scouting based on the one or two you miss in a weak year or you can gauge your head of Scouting based on their entire body of work. Timmins entire body of work is better than any GM in the last 10.