Any defendant, or any witness, in any civil action brought under the provisions of this act¹ may be required to testify, and any defendant, or any witness, may, upon proper process, be compelled to produce his books, records, invoices and all other documents of any such defendant or witness into court and the same may be introduced as evidence, but no defendant, or any witness in such civil action shall be prosecuted or subjected to any penalty or forfeiture for or on account of any transaction, matter or thing concerning which he may thus be required to testify or produce evidence, documentary or otherwise, and no testimony thus given or produced shall be received against him upon any criminal proceeding or investigation.