LEOhopeful--
Usually, at most PD's, someone in the department (usually also a sworn officer) teaches a lot of the defense/tactical-realted training. If you are interested in this "stuff," you'll likely have to pay your dues (a few years) on the streets in patrol FIRST and then, if you have the appropriate training & experience, you may have the ability to get on board with the academy staff to teach recruits.
I don't know anyone on the Detroit PD and I do not know how DPD goes about moving people arround within the department to specialized positions such as an academy trainer. But, I feel reasonably certain that is generally likely what you can expect in regards to your question. That is generally the traditional method one undergoes.
By the way, did you ever check out that link in my other post? Just curious......
Best of luck.
Charlie
"Good and evil are present in this world, and between the two there can be no compromise" - President George W. Bush, in his farewell address to the nation.