I have some good books on threat de-escalation and communication, but none that I know of that focus specifically on the physiological signs.

Ok, from memory.

Nonviolent communication by Rosenberg

And crucial conversations by ... Grenny? And like 4 other authors.

Sorry for not having the exact authors right now, but those two were highly suggested to me by a nurse to keep us and others out of conflict. Whether verbal or physical.

SouthNarc from Shivworks.com is a goldmine of information.

Here's a 19 page PDF about managing unknown contacts MUCs. It covers what you're looking at.

http://triangletactical.net/wp-content/uploads/2014/03/sncontacts.pdf

It has been my experince that the first hint of trouble is usually the stare someone gives you before the fight starts. I don't know how to describe it but I sure recognize it. I have gotten to the point at work that 9 times out of 10 I canusually tell who is going to bother me just by the look they give me even before they get to me. I can also usually tell how serious of a problem that they are probably going to be. While this isn't fool proof it has been the best give away in my experience.

Another thing is are they taking deep breaths particularly noticeable in their nostrils flaring? This is often a sign of someone getting ready for a fight and getting oxygen into their system. Another is someone working their hands in and out of a fist.

Another weird one is when people start ditching clothing. That is another sign that a fight may be about to start.

Pacing around or just looking nervous is another. Especially if their hands keep moving back and forth for where a weapon may be.

As for that the FBI did a study on where the bad guys tend to keep their guns. Dead right is what it was called if I remember right. It is a great study if you find it.

In their waste band on the front not in a holster was the most common place to hide a gun. This isn't to say bad guys don't use other methods but that was the most common. Use of a holster was uncommon. It was often found males would have a female companion often carry their gun for them because it was felt if they got stopped the girl was much less likely than they were to be searched.

Some other things I look at, how is someone dressed? For example big coat that can hide a gun in summer is going to make me look at some a bit more than if they are wearing the same coat in the winter. Someone dressed like a gang banger is also likely to get more of my attention than the guy in the buisness suit. Some other things is wearing non work gloves in the summer or a ski mask or shades at night. I hope you get the idea I could go on and on.

Where are you at and what are you doing?  When I'm working on an ATM they guy wandering around aimlessley watching from behind the check stands with nothing but a cup of coffey in his hands makes me wonder a lot more about his intentions than the old lady who is walking 4 feet away pushing a shoping cart for merchandise. In short if you don't look like you belong I start asking myself questions.

A few thhings I have learned over the years. Hope this helps I may post a few others latter.

It has been my experince that the first hint of trouble is usually the stare someone gives you before the fight starts. I don't know how to describe it but I sure recognize it. I have gotten to the point at work that 9 times out of 10 I canusually tell who is going to bother me just by the look they give me even before they get to me. I can also usually tell how serious of a problem that they are probably going to be. While this isn't fool proof it has been the best give away in my experience.

Another thing is are they taking deep breaths particularly noticeable in their nostrils flaring? This is often a sign of someone getting ready for a fight and getting oxygen into their system. Another is someone working their hands in and out of a fist.

Another weird one is when people start ditching clothing. That is another sign that a fight may be about to start.

Pacing around or just looking nervous is another. Especially if their hands keep moving back and forth for where a weapon may be.

As for that the FBI did a study on where the bad guys tend to keep their guns. Dead right is what it was called if I remember right. It is a great study if you find it.

In their waste band on the front not in a holster was the most common place to hide a gun. This isn't to say bad guys don't use other methods but that was the most common. Use of a holster was uncommon. It was often found males would have a female companion often carry their gun for them because it was felt if they got stopped the girl was much less likely than they were to be searched.

Some other things I look at, how is someone dressed? For example big coat that can hide a gun in summer is going to make me look at some a bit more than if they are wearing the same coat in the winter. Someone dressed like a gang banger is also likely to get more of my attention than the guy in the buisness suit. Some other things is wearing non work gloves in the summer or a ski mask or shades at night. I hope you get the idea I could go on and on.

Where are you at and what are you doing?  When I'm working on an ATM they guy wandering around aimlessley watching from behind the check stands with nothing but a cup of coffey in his hands makes me wonder a lot more about his intentions than the old lady who is walking 4 feet away pushing a shoping cart for merchandise. In short if you don't look like you belong I start asking myself questions.

A few thhings I have learned over the years. Hope this helps I may post a few others latter.

Thank you.  This is a nice expansion of what was covered in the original link

I can't remember if it's in some of the links but the number 1 indicator of a pre assault for LE is a failure to obey verbal commands. I like having suspect's sit on the curb. If I tell someone to sit down and they start protesting the color codes go up etc.

I few years ago I had a gig that entailed picking up cash (over a grand in mostly small denominations) and computers at a bingo game in a bad part of Pittsburgh. This was a once a week assignment and on a regular schedule. Over time I got a good scan of the street characters that hung out and I even hired one or two of the regulars to help lug out the cases of hand held bingo computers and put them in my van.

One evening two new faces approached me and asked for a couple of bucks to get something to eat. these two didn't look underfed and were more muscular than was common. They were two close to me for comfort as I stood next to my van. I went from condition yellow to orange as I turned very quickly to the van and flung open the door, turned and reached into the van and grabbed a handful of change from the console and drew my J frame from inside my waistband as I turned to grab the coins.

I never showed my snubbie, but held it down by my leg as I handed the change to the closest "actor" and said "no problem man" as i handed him the change. This quick movement startled them and one remarked "you don't need to shoot a guy asking for spare change", even though I never showed the weapon. It was all about situational awareness and body language.

They took the change and walked away. I never saw then again and never had any more problems with my pickup at that location. Word had spread about my activities and that encounter was a probe into my ability to defend myself and the cash I carried. Criminals look for soft targets just as whackos look for gun free zones to commit mass shootings.

digiroc