Are you saying that if I teach a technique and someone hurts someone else using it later, then I am responsible? That sounds ridiculous, to me anyway.
I am not sure what the case would be in a dojo setting... probably much the same, I would think... but I am sure that in any kind of official setting such as law enforcement or security training, the trainer is definitely in the loop. He will almost certainly be named in any law suit in which the plaintiff's lawyer takes the approach that what was taught was either inappropriate i.e. it had a high inherent likelihood to cause injury or in the circumstance in which the technique was used it constituted excessive force (meaning you didn't train the properly when it was ok to use the technique). Either way, the defendant will attempt to prove that he executed the technique as instructed, it was used according to the use of force training he received, and that he did not violate policy when he used the technique.
As the trainer, you are small fry in a law suit. The lawyers want to tie in the actions of the officer with negligence on the part of the department. The trainer is just in the middle. In a dojo it would be a bit different depending on how you structured the business. Many dojos are sole proprietors. In that case you are personally in the loop. If you have teachers doing classes for you, you could find yourself in a lawsuit based on something they taught, since you could be considered negligent for not properly supervising your instructors. If you didn't supervise them you are liable because you were negligent by not doing so. If you did supervise them, in other words, you set up the curriculum (or your organization did), you and your organization could easily be liable if something you taught in class was used to injure someone.
If you are teaching a technique which is inherently dangerous, even in the dojo where people are trained to take ukemi, then that technique is probably a high level force technique, perhaps even deadly force, if used on a non-training subject. So if one of your students goes out to a bar and whips that technique on a subject when the circumstance did not fully justify that level of force, you could easily be in the law suit as having taught something inherently dangerous and failed to properly explain the risks involved and what level of force that particular technique represents.
If you can't honestly say that your students could place each technique in your curriculum in its proper place on a continuum of force, or, more likely, your students don't even know what a continuum of force is, than you could expect to be included in any excessive force law suit naming your student if they hurt someone using one of the techniques you taught.
The only real protection for most of us is that we simply do not have much money. Litigators are looking for the big bucks usually, unless you have a local ambulance chaser, in which case he will be looking for an out of court settlement. Here in the Seattle area, a department will ordinarily settle automatically for anything 40 thousand or less. I had a friend who had his climbing school go out of business after a kid, disobeying instructions, unclipped from his protection and fell off a boulder and broke his arm. My friend's insurance company paid out damages and then raised his rates so high he closed the school. All this even though it was clearly the kid's own fault. It didn't matter.
The good news is, it is highly unlikely that any of our students will ever use a technique we taught for self defense. If they did. it would probably be justified, in which case there is no liability. But we are definitely potentially in the chain of responsibility if a student misuses something he's taught or it even appears that he might have. If your are sued, you are screwed even if the plaintiff isn't justified.