Hi Vamp!
A body cam can be a great idea. I have used a GoPro clone for this.
Do you want to be able to see what the camera is seeing, in real time, and control it? Such as with a phone wifi or Bluetooth connection? Or would you be content with a completely passive camera, for review later?
There are some very inexpensive HD cameras that have IR night vision, but no real-time monitoring.
You will also need IR illumination for a night vision body cam.
A regular, daylight bodycam can be used for investigating, but you will need white light illumination for those.
Some mini IR cameras have built--in illuminators. Trust me- they are NEVER bright enough, on their own.