[Bruno]

Originally Posted by Ashtagon

It is never any kind of mercy killing if the patient resists!

Not exactly, although that is generally a safe statement. Certainly, a "patient" who's resisting in an organized fashion or e.g. able to scream "Get off me you bastard!" or "Help help!" is not a candidate. "Resistance" isn't always a higher brain function, however.

Brain injury can cause paradoxical violence (basically, Berserk + Bad Temper as a consequence of brain swelling). It's an issue particularly notoriously with motorcyclists thrown off their bikes at speed but being lucky enough to survive. You can end up with someone who is going to die from that brain injury if they don't get treatment, and is one bad jolt away from permanent paralysis from vertebral damage... and he's biting and punching and kicking and screaming and headbutting anyone who comes near him.

The complaint with paramedics and ER staff is that these people always seem to also be the big scary looking guys, but I think that's a bit of bias.

If you're in the kind of environment where you can't get the patient safely subdued and to a surgery, then they may be pretty darn "dead man walking" (and swinging fists), depending on other injuries. A decision whether to euthanize this patient in e.g. a battlefield situation, in enemy territory on a stealth mission, or if the patient is just that flat-out-dangerous even with lethal injuries might have to be made.

While well-co-ordinated and -thought-out violence requires a fair amount of functioning brain, if the fight-or-flight system gets jamned "on" and set to "fight" you can get someone who "resists" everything. It's not that they're making a decision to resist you, because they have no idea what you are or what you're doing and whether they're interested in it. It's basically "I hurt => everything's fault => hit everything".

This unfortunately happens with other kinds of brain damage as well (re: dementia). It's usually more intermittent, but these are also situations where family members may start discussing euthanasia with attending physicians. The patient may even bring the subject up, although generally by this point you end up in a whole other argument over whether the patient is competent any more.

You can also get this sort of not-coherent violence with other ways you mess up your brain, ie chemicals (either internal brain chemistry, or by adding chemicals that have no business being there). This sort of patient isn't a euthanasia candidate, even if they're currently wearing a gurney like a backpack while fighting a security guard (true life ER stories!).

EDIT:

Originally Posted by Ashtagon

Also, why do you have an actual innocent as someone you want to kill?

In the case of the jackass munchkin trying to weasel their way out of Cannot Harm Innocents: these kinds of players rarely need deep reasons to murderdeathkill NPCs. Why this player would take CHI as a disadvantage if they meant to stab everyone? I presume because either the GM made them (part of a template or lens, or just flat out made them) or as some sort of poorly-thought-out-scheme to get more points. Or they're normally better tempered but the player is angry/drunk/etc tonight and taking it out on irritating but "Innocent" NPCs.

The character, on the other claw, might have a certain excuse as being a clearly Bad Person who's been "cursed" with Cannot Harm Innocents by someone trying to improve their behavior (via mind control, magic, brain-washing, what-have-you).