19 U.S.C. § 537 — Officers, informers, and defendants as witnesses

This section covers who may testify as a witness in a court case about recovering, reducing, or canceling a fine, penalty, or forfeiture under Act of June 22, 1874 (chapter 391, 18 Statutes 188). Normally, someone who stands to personally gain money from a case's outcome might be barred from testifying as a witness in it. This section removes that bar for a specific group: any officer, or other person, who is entitled to — or is claiming — compensation under that 1874 Act. Being entitled to or claiming a share of a fine, penalty, or forfeiture does not disqualify that person from becoming a witness in the action seeking to recover, reduce, or cancel it. Such a witness can be examined and cross-examined just like any other witness. And testifying does not cost them any right, title, share, or interest they otherwise have in the fine, penalty, or forfeiture at issue — they don't give up their claim by testifying. The section also allows the defendant or defendants in such a case to appear, testify, and be examined and cross-examined in the same way as other witnesses.