HRS §621-5
Witnesses present in court can be called to testify
During a trial or hearing, anyone present who is legally allowed to testify can be called to give evidence or produce documents, even without a subpoena. If they refuse, they face the same penalties as if they had been formally subpoenaed.
everyone
The statute, as written — Bystanders called without subpoena
On the trial of any issue, matter or question, or on an inquiry arising in any action or proceeding in any court or before any person having authority to hear, receive, and examine evidence, any person who happens to be present, and who by virtue of this chapter is competent to give evidence may be called and required to give evidence and to produce any document. If any such person when called and required as aforesaid, does not appear and give evidence and, if then able so to do, produce the document, the person shall be subject to the same proceedings and liabilities as if the person had been duly served with a writ of subpoena ad testificandum or duces tecum.
LawTrove is not legal advice. The summary above is a computer-generated restatement — the authoritative text is the official version linked above.