There are significant restrictions on the use of a command investigation, such as an AR 15-6 report, as evidence at a court-martial. The primary restriction is the rule against hearsay. The investigative report itself is an “out-of-court statement” that contains other out-of-court statements from witnesses. Therefore, the report and its contents are generally inadmissible as evidence to prove the truth of what is contained within them. The prosecution cannot simply introduce the 15-6 report and rest their case.
Instead, the command investigation is used as a starting point. The prosecutor must call the same witnesses who were interviewed during the 15-6 investigation to come into court and provide live, sworn testimony. The defense attorney then has the right to cross-examine these witnesses. The findings and recommendations of the investigating officer are also inadmissible, as they are simply the opinion of one person and would invade the province of the court-martial panel, whose job it is to make their own findings.
A military defense attorney will object to any attempt by the prosecution to introduce the command investigation report itself as substantive evidence. The attorney may, however, use the report for their own purposes. For example, if a witness’s live testimony at the court-martial contradicts what they said in their sworn statement to the 15-6 investigator, the attorney can use that prior inconsistent statement from the report to impeach the witness’s credibility.