Terri Shiavo was starved to death by others based upon nothing more than hearsay. When a person is starved to death by someone else we call that murder in our society. That she needed assistance to be fed and to take water does not in any way diminish what was done to her. She was deprived of nutrition and water - literally starved to death - by someone other than herself. That, bottom line, shouldn't be allowed in any civilized society regardless of what you think you might want done in case something happens to you.
The reality of the situation is that none of us has any idea of what Terri's life, or our own, would be like under those circumstances. She could have been happier than she'd ever been before and no one had any way of knowing it. She breathed, her heart was beating on its own. She metabolized food and generated waste. She was indeed alive and no one who is being intellectually honest can say they know for certain what her life was like before she was starved to death by doctors at the request of her husband. The intentional destruction of human life in any form ought to be abhorrent to everyone with above room temperature IQ while we remain ignorant of how the human mind actually works. Brain dead individuals can't breathe on their own, as Terri could. Their hearts do not beat without assistance, as Terri's did. Terri was not allowed to die, she was intentionally killed by starvation.
If'n you are serious about the "DNR" tattoo, then you should put it square in the middle of your chest where it will be seen when they seek to attach the diodes to you to record your heart rate and breathing rate.
