Everywhere he looked — in the classroom, out on the driving course, at the shooting range — Casey Canfield saw youth.

Not that he was some over-the-hill trainee who didn’t belong. Not by any means. But pushing 40, at an age when many people are knee-deep into their careers, Canfield was trying to launch his among fellow police academy students 10 to 15 years younger than him.

It was a great motivator.

Two years of law enforcement training crammed int...