Indoctrinated or not, they're still dying willingly for a belief.

Is it possible to go willingly to *certain* death for a belief without having been indoctrinated in some way at some time?

Of course, religious martyrs see death differently from the rest of us. They "know" they're headed for something better, so death becomes no more than an extreme test of faith and courage.

The overall value or relative sanity of belief doesn't matter. You've got your martyrs, your suicide bombers, your falsely accused witches, your kamikaze pilots, your IRA hunger strikers, and your Heaven's Gate types. I'm sure I've left some out. But it's quite a mixed bag. And some people - like soldiers who throw themselves on grenades - are acting so reflexively that the idea of an abstract "cause" (instead of the lives of others nearby) doesn't apply.

Falsely accused heretics who wouldn't "repent" were caught in a   double bind. If they swore falsely that they'd forsaken God, and saved themselves, God might send them to hell later for having sworn falsely. Dying now to prove their innocence forestalled that possibility.

But since the "cause" they were dying for was their personal salvation rather than some presumed public good, they seem to be in a special category too. The Jamestown and Heaven's Gate people didn't have much time to think it over, and may have been more sheeplike and disoriented than idealistic. That may put them out of the discussion too.