Hi Bernard
This is what struck me:
Your 'audience' are Professional Policing degree students. Therefore this should be interesting and crucial topic for them. If they will shortly be responsible for arresting people correctly, they should be interested. If they're not, something is very wrong.
I'd think of the topic in terms of Skills, Knowledge, Attitude and Awareness and create your objectives along those lines. That will give you a clearer idea of what you want to achieve. It will also show you what can be realistically achieved.
One you've done that, you have to decide which 'tools' you have available and which of those will help the students best. (Personally, I wouldn't use 'realistic scenarios', I'd go for actual case studies as these are, in my view more pertinent, and scenarios can become forced an inauthentic).
It actually looks like a really interesting topic to me, so perhaps the trick is not making the training dry.