Actually, you got me on a typo there. I'll edit. It's meant to say "would be considered an act of murder."

However, I still consider a mercy killing such as that to be justifiable, because it puts someone out of years of misery, despite the fact that you are taking a life. The case with Schiavo dealt largely with the fact that she was essentially a vegetable, for lack of a better word. She was unable to pull the plug for herself, let alone communicate with anybody on even the most primitive of levels (blinking, moaning, etc), while showing zero signs of recovery for years. In order to give her final rest, a move HAD to be made by someone to forcibly take her life (though it's debatable if she were truly alive in the first place), because she could not herself. The act of pulling the plug and stopping the machines that allowed her to live, is an act of murder. However, in such a circumstance, I view it as justifiable because it is providing a woman with peace and ending her long suffering.

Though, each situation is just that, it's own individual happening; and what may be considered mercy for one, may not for another.