In the trial of complaints, informations, indictments and other proceedings against persons charged with crimes or offenses, the person so charged shall, at his or her own request and not otherwise, be deemed a competent witness. The credit to be given to his or her testimony shall be left solely to the jury, under the instructions of the court but the failure of such person to testify shall not be a matter of comment to the jury by either the court or the prosecutor and shall not be considered by the jury as evidence against him or her.