SPOILER - How did he get away with it?

I was wondering the same thing, poisoning would be very easy to detect.

He murdered him??

I'm proud of Mac for killing that POS father of his. He should've been given Nobel Prize for it. Abusive parents deserve the WORST.

I guess that was not the focus of the movie. Just the fact that he did kill his father and have to carry that guilt with him for so many years. But I agree.....I didn't shed a tear when Dad died.