Art. 440 Administration of oath to witnesses

Before anyone testifies in front of a grand jury, the foreman must swear them in first. The witness has to promise two things under oath: to tell the truth, and to keep secret whatever they hear or learn during the grand jury meeting.

This secrecy promise is a big deal. Grand jury proceedings are private, and witnesses aren't allowed to share what happened in that room with others, unless the law specifically says they can. This rule exists so grand jury investigations stay confidential and witnesses take their testimony seriously from the start.