I am not sure how many martial artists have had to restrain a person before outside dojo conditions. The dojo can get rough as it is, but the real world problems are often difficult to divine.
Let me introduce some of my experiences. From the mid to late 1990's I worked in residential treatment centers. They were a motley mix of highly intelligent criminally inclined gang youth. The facility members were all low pay with high staff turn over. The staff shared power with the youth - barely, which is a bad recipe. The institution had a bad system. The youth were intelligent and bored. They were strong from seemingly non stop push ups. Violence in some form was part of everyday life in the residential treatment facilities. Power struggles were the day to day operation. Sadly due to the circumstances that we had to work in, restraints happened often. In some places I worked I participated in them several times a day. One day I recall I did something like 6 restraints. It was a bad deal, but I learned a lot of valuable lessons in those times.
Restraints Take Time
If you are going to take away someone's ability to move, the process of keeping them on the ground is going to take time and energy. Whether you move in arrest techniques to keep them permanently detained or if you are simply going to talk the person down from their anger, be prepared to spend some time with the person. In the incident I got into with the drug crazed maniac early this year, I spent a good 20 minutes keeping him pinned, then another 25 minutes moving him off premise to the waiting hands of the police.
Catch and Release
So now you find yourself pinning someone down. Now what? You have to let them go eventually. Of course how you do this depends on the situation but usually there is a period of negotiation. You have to give a person their freedom back in stages, as they demonstrate to you they have regained control of themselves. Let freedom become their choice.
Here is a sample dialogue of how to release a person from a hold. Of course the situation ALWAYS varies. This dialogue might be enough in real life, or it might take twenty minutes. But the conversation is a negotiation, and you have to respect the other person's rights and powers in the conversation.
pinned guy - You stupid *@#$%^^&&** I'll kill you!
Budo guy - Well looks like you have two choices, I break your arm or I let you go. Which do you want?
pinned guy - eat $#@%#^#.
Budo Guy - the broken arm then??? (tightening hold)
pinned guy - ok, ok, ok....
Budo Guy - ok what? Do you want your arm broken or to be released?
pinned guy - *^%$#$@ let me go!
Budo Guy - Ok I will let you go, but you have to show me you are calm. Are you calm?
pinned guy - I'm $#@%%#%^& calm
Budo Guy - No swearing. You don't sound calm to me. Are you calm?
pinnned guy - I am calm...I am calm.
Budo Guy - Good. I am going to relax my hold on your elbow here. I want you to remain cool. If you start going acting crazy again I am gonna snap it in tight again and it might break this time. You don't want that do you?
pinned guy - no
Budo Guy - (relaxing hold) there. Feel better?
pinned guy - yes
Budo Guy - look I really want to give you your arm back. But here is the deal. I can't have you acting all crazy. I really want to trust you. Can I trust you?
pinned guy - yes, you can trust me.
Budo Guy - Great. I am glad you are talking with me now. Here is the deal. I am going to trust you. I am going to put your arm beside you, to get all the tension off of it. However, you got to just lay there for a minute and talk with me. After I trust you are cool again, I am going to go buy you a beer and we are going to laugh about this ok? However If you acting a fool again, we are going to tangle and I am in a better spot here buddy. I don't want that. let's be cool ok?
pinned guy - cool.
Budo Guy - Here is your arm back. It might be a little sore tomorrow but no real damage. Just lay there for a second and relax. In a minute we are going to get that beer and everything is kosher right?
pinned guy - right.
Notice I am trying to keep the conversation tight and controlled. I ask questions at the end of every statement. I am giving him choices and power with every correct response, and making things worse with every incorrect response. He chooses his own destiny. Be cool. Be respectful. Steer energies towards the positive conclusion no matter how big of a schmuck the guy is.
Hope this helps! May you never have to restrain another person!