Warning for disgusting content 37s long surveillance video of Man walking up to someone and emptying a cup of contents from toilet. https://www.youtube.com/watch?v=IjDfJlsyXj4
Are you allowed to use lethal force to prevent this most disgusting act? Any jurisdiction you wish to answer from. Especially for someone without access to non-deadly force.
There are many questions on this site asking about the acceptability of a particular act or deadly force taken in self-defence:
The answer is always the same. It depends on whether the response is reasonable or proportional (precise expression varies depending on the jurisdiction).
In Canada, for an act to be permitted as self-defence it must, among other things, be "reasonable in the circumstances" (Criminal Code, s. 34(1)(c)).
In determining whether the defensive act is "reasonable in the circumstances," the court must consider all the circumstances, including, but not limited to "the nature and proportionality of the person's response to the use or threat of force" (s. 34(2)(c), (g)).
This is a case-by-case assessment left to the trier of fact (a jury, where there is one, or a judge, when sitting alone). I can find no example in Canadian law where the circumstance you describe was responded to with intentionally lethal force. I predict that, without more, no trier of fact would find intentionally lethal force to be reasonable in the circumstances, largely because of the lack of proportionality such response.
I also note that "a person defending [themself] against an attack, reasonably apprehended, cannot be expected to weigh to a nicety, the exact measure of necessary defenceive action." Actions taken reasonably, without the intention of killing someone, may still end up killing someone, and nonetheless be permitted due to self-defence.
