Kalkines or Garrity; a legal question.

So, I was looking over some legal stuff on wikipedia, and one link lead to another, and I found out about Kalkines Warnings and Garrity Warnings:

http://en.wikipedia.org/wiki/Kalkines_Warning

http://en.wikipedia.org/wiki/Garrity_Warning

They seem pretty similar, except for the ‘voluntary’ part. Anyone able to enlighten me as to when one would be (legally) used as opposed to the other?

Well, the Kalkines warning advises those being questioned of their immunity to criminal prosecution, and that they may be fired for not cooperating; the Garrity warning advises those being questioned that they won’t be fired or disciplined for not answering, but that they may be prosecuted for anything they say. So they’re pretty much opposites. I have no personal knowledge of this, but it would seem that the Garrity warning is directed at suspects, whereas the Kalkines warning is directed at witnesses.