Thanks for the replies.

My only lingering question is, how is danger of this person judged?

Anyone can say they want to kill. I'd assume they ask if you tried, or have the supplies. Even if one hasn't/doesn't, how can you analyze ones thought process to see if at risk? I would guess, frequency of thoughts? Duration?

And another point - What if these thoughts were persistent for a couple years? What if it is just, who you are, rather than a symptom that can be controlled? Why go to the hospital only when fear of acting out, as opposed to when the thoughts started?