I don’t have any law cases at hand, but generally speaking pepper spray/mace/taser is not considered lethal force.
If pepper spray/mace/taser is part of a larger effort, specifically in offensive use rather than defensive use, then it can be considered lethal force.
If you use pepper spray/mace/taser to incapacitate someone who has a firearm, you have not only rendered them unable to defend themselves, but you now also have access to their firearm.
And if you take their firearm then:
- You have removed a defensive tool from that person
- You now have a deadly weapon
- You have shown your intent to harm (by attacking them in the first place). The best predictor of future behavior is past behavior especially behavior that just happened.
There are a bajillion cases where people take a firearm from a police officer and then shoot them with their own firearm.
So taken under the totality of circumstances (which may or may NOT apply to this specific case), you have a very likely scenario of attempting to take someone’s firearm with the intent to use it immediately on that person (very likely) or at some later point.
Other examples would be if you are strong-arm robbed (no weapons) and you worry if they pat you down they will find your firearm and take it from you.