Polyjuice Potions... Dead or alive?

[gopotter2004]

No: HPFGUIDX 59193

Now, I realize that Crouch, Jr. had to keep Moody alive to get hair 
and ask him questions and such like that. But was it indeed 
necessary to keep him alive in a potion sense? Couldn't you just 
keep a few finger nails (already dead anyway) of anyone dead, and 
pop them in for a quick-use potion? Sure, you would have a limited 
number of times to make the potion before using up the supply, but 
how confused would Harry be if he met his father, or mother? He 
would probably know it wasn't them, but he would want so badly for 
it to be, it would probably throw him off pretty badly. Just a 
thought.

Becky