What are the differences between Army CID 31D Special Agent and Army civilian CID Special Agent?

I don’t believe it’s as simple as doing a reclass. They only take the best of the best through the application process from the military police community. I have also heard rumors that the Department of Army may reorganize CID more like the NCIS model or possibly transfer it to civilian control instead of the Provost Marshal.

Regarding your initial question, nothing on first blush. The civilian agent does not have to worry about violating the Posse Comitatus act (military used to enforce civil law). The fine print of the act deals only with arresting civilians. The civilian is not military under the definition of the act, thus the civilian agent can make an arrest under an arrest warrant or without a warrant on crimes committed in their presence. I was a 31D (when it was a 95D) for three years and a 311A (when it was 951A) for 14 years. I routinely investigated civilians for crimes committed against the Army, on Army installations. I sought federal and state search warrants, completed search warrant affidavits and testified before state and federal grand juries. I left arresting civilians to the FBI or the US Marshal Service. Military agents and their civilian counterparts apprehend military personnel.

31D is a communication MOS not CID?