I have suggestion that may improve your game!
1. Add guns
2. Add calls such as bank robbery, hostages, and ETC.
3. Add multiple kinds of police officers when your rebirth such as SWAT and ETC.
4. Add events! Every 30 minutes will be a event. Events could help the game more!
5. Add more entertainment other than just sending the prisoners to the mining section for a several seconds. The prisoners also could have guns to fight back. If they kill the officer, more officers will arrive. Some will have guns.
6. Have fun! I hope this list of suggestions will help you!