§146.  Discovery; incrimination

The witness shall not refuse to produce books or papers in accordance with the order or to answer any questions in reference to the subject matter of the investigation upon the ground that these acts would tend to incriminate him or subject him to a penalty or forfeiture.  

The witness shall not be liable to prosecution, or subject to any action, penalty, or forfeiture on account of any transaction, matter, or thing concerning which he may testify or produce books or papers.