Office of the Inspector General - Investigations

Army

According to AR 20-1 para 7-1a.

“Investigations as an inspector general function. Investigations is the IG function that provides the commander/di-recting authority another means through which to resolve allegations of impropriety. The primary purpose of IG investigations and investigative inquiries is to resolve allegations of impropriety efficiently and effectively by gathering evidence, evaluating the credibility of that evidence, analyzing that evidence in the context of identified standards, and packaging that analysis and subsequent conclusion in a well-written report. In this regard, IGs may investigate violations of policy, regulation, or law; mismanagement; unethical behavior; fraud; or misconduct. However, IGs will provide the command the opportunity to resolve allegations within command channels. Therefore, IGs will refer all command-appropriate allegations to the command in accordance with guidance from the directing authority or, if criminal in nature, to CID. Directing authorities should opt for an IG investigation or investigative inquiry when extreme discretion is necessary or when the command investigation is not likely to be efficient or effective. Once an IG initiates an investigation or investigative inquiry, the IG will complete the entire investigative action to determine if the allegations are "substantiated" or "not substantiated" (see para 7–2b, below) and if any issues are "founded" or "unfounded" (see para 6–1a, above).”

Air Force 

AFI 90-301
4.1.2. IG investigations are administrative in nature--they are fact finding rather than judicial proceedings. Preponderance of the evidence is the standard of proof.
4.2.2. Not all matters are appropriate for the IG, nor are all matters relevant to the Department of the Air Force. Most Department of the Air Force processes have embedded appeal procedures that provide complainants with due process, and should be used as the best avenue for resolution.