A witness has a privilege to refuse to disclose a communication made to a grand jury by a complainant or witness, and evidence thereof is inadmissible, unless the judge finds (a) the matter which the communication concerned was not within the function of the grand jury to investigate, or (b) the grand jury has finished its investigation, if any, of the matter, and its finding, if any, has lawfully been made public by filing it in court or otherwise, or (c) disclosure should be made in the interests of justice.
K.S.A. 60-435