So, persons (A) & (D)are having an argument, person (A) is becoming very heated in defence of their viewpoint, swearing a lot, insulting person (D's) family etc. I'm sure you know the situation. Person (D) becomes concerned for their safety, but person (A) has given few physical indications of violence other than waving their hands around a lot like a windmill. (Cut off some peoples arms and they can't talk, I'm sure you know what I mean). Now, how can you restrain person (A) if they haven't given you a physical opportunity to do so? IE, they haven't gone to punch you or to kick you.

it all comes down to "Perceived Threat", and then you have to convince the jury later. without any verbal or physical threatening behaviour towards you it would be hard to justify it. we all have different levels of self confidence and someone with little confidence may feel threatened earlier than others, but man A is still the same in action. the key comes from A actually saying something or doing something that would be viewed as a precursor to attack. insults are not enough. its a tricky road, but just remember not to let them get close and you should be ok.

be very careful about 'restraining' people as they have had to have broken a law for them to be held. because rights allow us all the freedom not to be held unless a law has been broken. if they have broken no law, yet you think they have and restrain him, you are in a lot of trouble. if he threatens you with harm, and you manage to subdue him, you need to phone the police fast as you can only hold someone with the intent to hand them over to the police. and they must have a clear airway. pain isnt so much a factor as their breathing. if they are screaming, then they are fine. tell them you are holding them till police get there.

and ALWAYS be the calm one when the police turn up. you are more credible.
everyones an expert on the internet. lol