You can easily get this in the very first mission Donut Shop. You may need to have your health upgraded slightly. As you enter you should be able to arrest the first enemy easily enough as he is by the door you enter through, you can lure enemies towards the door by alerting them and then pressing
to arrest them. After you've arrested the first 2 enemies another one is in the next room and will remain there if not alerted by the first 2. Once he is arrested you have 3 enemies left in the next room where the Chef is and you can run in and alert them then fall back and allow them to come to you. If you die you still have another Cop available to carry on the arrests as long as you leave him or her back at the beginning of the Mission.