One great lesson that I've learned from the co-lead instructor of the USKMA, Brannon Hicks, is to ask "Is this person rational?" He leads a great RBT class and when critiquing a scenario the question he asks over and over to the officer is "Was this a rational person?" Thinking in those terms helps the officer to make decisions much quicker.
I taught a third-party protection class recently where one of the scenarios was that they were walking a spouse/significant other and a belligerent person came up threatening the spouse. The student playing the belligerent person never laid hands on the spouse but kept coming forward and yelling threats over and over. Because there was no actual contact many of the students were confused on what they should do. After the scenario I would ask them "Was this a rational person?" Would a rational person be belligerent, keep coming forward even though you've tried to walk away and threaten to do harm to another person? When the answer was "no, this is not a rational person." the solution seemed to show itself. It is not rational to threaten a stranger and to keep coming forward as if to do harm. My thought was if I know this isn't a rational person and I have clearly try to get away and leave the situation and de-escalate, if that person keeps coming forward I probably need to strike first. I can justify in my head, and in a court of law, that I believed this was not a rational person, they were threatening to do harm, and I was not going to wait on them to draw a knife or to follow through with your threat. Again, I would have witnesses stating that I was doing the rational thing. I was trying to leave I was trying to de-escalate I was trying to break contact with this person
SGT Hicks shows a video of a law-enforcement officer who waits way too long to put hands on a criminal. The first thing the officer does is point a taser at the man and tell him to stop coming forward. The man continues to come forward. If this officer would have just thought "This is not a rational thing. I am a law-enforcement officer giving a command and pointing a weapon at this person and yet they keep coming forward". If he would have decided right then and there that he was dealing with an irrational person and did something about it it would've saved him a lot of trouble. It ended up that this criminal drew a knife and stabbed the officer and the officer had to shoot and kill this man.
In my mind setting I tell myself over and over to ask that simple question. Is this person rational? Again, a rational person would not threaten a stranger, act violently, put himself in my face, or any other such thing. Unless we thought about this in our heads ahead of time we may end up frozen thinking "Why is this person doing this, do I know this person? I need to de-escalate this, I need to keep giving orders, keep giving commands, I need to talk my way out of this." It goes without saying that you're not going to talk an irrational person out of anything. In my opinion, it is time to go hands-on if I've tried to leave, de-escalate, etc. and it's not working. Any rational person is not going to do the expected. An irrational person is a dangerous person.
In any situation ask yourself that question. Is this person being rational? If they are rational we can talk. If there irrational it may be time to go hands-on. Be safe!