AR 190-30 governs Department of the Army policy and procedures for military police investigations and the MPI program.
View AR 190-30 on armypubs.army.mil
It covers the selection, training, certification, employment, credentials, and investigative authority of military police investigators and Department of the Army civilian detectives and investigators. It also addresses investigations, evidence, records, polygraph activities, electronic equipment, and case folders.
Training and assignment as a MPI is not a reenlistment option. (paragraph 2-1)
The only authorized credentials for MPI are DA Form 3837 and DA Form 38371. (paragraph 2-1)
Reproduction of MPI or DAC credentials or use of locally produced MPI or DAC identification documents is prohibited. (paragraph 2-1)
MPI and DAC detectives/investigators have authority to make apprehensions in accordance with Article 7, UCMJ; Rule for Courts-Martial 302 (b)(1), Manual for Courts-Martial, United States 2002 (Revised Edition). (paragraph 4-11)
Recordings, which contain conversations described in this section, will be retained for a period of 60 days. (paragraph 4-24)