I’ve conducted 3 15-6’s during my time in and I found that it wasn’t necessary to prepare before hand. When you receive the appointment orders to be an IO, you will have to schedule a legal brief with a JAG officer who will set you up with the information you need to conduct the investigation. The JAG officer will also probably have a submission format for your 15-6, that will guide you how to put the packet together.

However, if you want to get ahead on being an IO, here’s the how to guide that my Brigade Judge Advocate directed me to use during my first 15-6 investigation. I hope that its helpful in giving you the basics.

http://www.jrtc-polk.army.mil/SJA/Documents/15-6_IO_%20Guide.pdf

Let me know if the above document answers your questions or if you have any questions about what the experience is like.

-David