RSA 7:27: Testimonial Privilege.

No person shall be excused from testifying or from producing any book or paper in any investigation or inquiry by or upon any hearing before the attorney general, when ordered to do so by the attorney general, upon the ground that the testimony or evidence, book or document required of him may tend to incriminate him or subject him to a penalty or forfeiture; but no person shall be prosecuted, punished or subjected to any penalty or forfeiture for or on account of any act, transaction, matter or thing concerning which under oath, after claiming his privilege, he shall by order of the attorney general have testified or produced documentary evidence.