As an occasional viewer of COPS, I have seen this many times. A guy in the back of the police car starts banging his head against stuff...so they pull him out, add leg restraints, and lay him in the back seat unbelted.
Wise or not, its a common practice. The defense should call up the police chief, deputy chief, and down the line...and ask if they ever transported a prisoner unbelted.
If its a normal practice, its hard to call it 2nd degree murder.
It sounds like they stopped several times, and at some point the guy stands up, and perhaps that’s when he was injured seriously.
I fail now to see how this is a homicide or reckless homicide or manslaughter or anything, and I bet that if they take the testimony of each individual cop, they will all tell the same story and not throw each other under the bus.
In other words, this was an unfortunate outcome, but it happens.