An opinion of the medical review panel shall be admissible as evidence in the action brought by the plaintiff, but shall not be conclusive. Either party shall have the right to call, at his cost, any member of the panel, except the judge, as a witness. If called, each witness shall be required to appear and testify. The panelist shall have absolute immunity from civil liability for all communications, findings, opinions and conclusions made in the course and scope of duties prescribed by this chapter.