(a) Whenever in the judgment of the Chief State’s Attorney, a state’s attorney or the deputy chief state’s attorney, the testimony of any witness or the production of books, papers or other evidence of any witness is necessary to the public interest in any (1) criminal proceeding involving narcotics, arson, bribery, gambling, election law violations, felonious crimes of violence, any violation which is an offense under the provisions of title 22a, corruption in the executive, legislative or judicial branch of state government or in the government of any political subdivision of the state, fraud by a vendor of goods or services in the medical assistance program under Title XIX of the Social Security Act amendments of 1965, as amended, any violation of chapter 949c, or any other class A, B or C felony or unclassified felony punishable by a term of imprisonment in excess of five years for which the Chief State’s Attorney or state’s attorney demonstrates that he has no other means of obtaining sufficient information as to whether a crime has been committed or the identity of the person or persons who may have committed a crime, before a court or grand jury of this state, (2) investigation conducted by an investigatory grand jury as provided in sections 54-47b to 54-47g, inclusive, or (3) delinquency proceeding the Chief State’s Attorney, the state’s attorney, or the deputy chief state’s attorney, may, with notice to the witness, after the witness has claimed his privilege against self-incrimination, make application to the court for an order directing the witness to testify or produce evidence subject to the provisions of this section.

(b) Upon the issuance of the order such witness shall not be excused from testifying or from producing books, papers or other evidence in such case or proceeding on the ground that the testimony or evidence required of him may tend to incriminate him or subject him to a penalty or forfeiture. No such witness may be prosecuted or subjected to any penalty or forfeiture for or on account of any transaction, matter or thing concerning which he is compelled to testify or produce evidence, and no testimony or evidence so compelled, and no evidence discovered as a result of or otherwise derived from testimony or evidence so compelled, may be used as evidence against him in any proceeding, except that no witness shall be immune from prosecution for perjury or contempt committed while giving such testimony or producing such evidence. Whenever evidence is objected to as inadmissible because it was discovered as a result of or otherwise derived from compelled testimony or evidence, the burden shall be upon the person offering the challenged evidence to establish a source independent of the compelled testimony or evidence.