Nice thought, but, to me, getting a Criminal Justice degree and the loan debt isn't worth it if you're already a cop (unless you plan to go into the FBI). If you're going to invest the time and energy to work a full time job that has loads of mandatory OT and carry a full course load, get a degree in something that will help you in your new career after you retire from the force.
You don't want to get to retirement and realize you have nothing to fall back on.