Should a person who kills a child-rapist go to jail?

Global Warming...

Who would you trust to fly a plane that you're going to ride in? A pilot who is able to learn how to fly quickly and is a 'natural' or a pilot who probably need to take extra time to learn it and is not a 'natural'?

Imagine yourself as a doctor treating a terminally ill patient, whose condition has recently become dire. Provided that you are not required by law to do so, would you tell the patient that he/she is going to die?