I'd be tempted to split it into two types:
Animal handler, unlocked through Bureaucracy, after Chief. Gives access to:
- High health (in relation to sniffer dog, low health in relation to humans)
- Runs faster than prisoners and guards
- Large visibility radius (more than guards)
- Will attack prisoners on sight; causes injury to prisoner; slows prisoner when attacking (to less than walking speed)
This last part is key. You don't want to put Attack dogs amongst your general population, but you might want them in buffer zones to stop escapees.
Prisoners will defend themselves when being attacked by dog, will cause injury to dog.
- Low health (in relation to attack dog)
- Runs at same speed as prisoners and guards
- Medium visibility radius (more than chef/workman, less than guards)
- Will identify prisoners with contraband, similar to metal detector. (if drugs are introduced, this would be to identify drugs; whereas metal detector to identify weapons)
Prisoners may attack dog when no guards present, causing injury to dog.