No person adduced as a witness shall be excluded from giving evidence by reason of having been convicted of or having suffered punishment for crime, or by reason of interest, or by reason of agency or of partial counsel, or by reason of having appeared without citation or without having been duly cited to attend, or by reason of having been precognosced subsequently to the date of citation.

Every person so adduced, who is not otherwise by law disqualified from giving evidence, shall be admissible as a witness, notwithstanding any objection offered on any of the above-mentioned grounds.

Nothing in this section shall prevent such witness from being examined on any point tending to affect his credibility.

Where any person who is or has been an agent of the accused shall be adduced and examined as a witness for the accused, it shall not be competent to the accused to object, on the ground of confidentiality, to any question proposed to be put to such witness on matter pertinent to the issue of the guilt of the accused.