Section 67. The chief justice of the Boston municipal court department may appoint such official court interpreters, or enter into such service contracts for the provision of telephone-based interpretation services, as he may deem necessary for the criminal and the civil sessions of the court, subject to the approval of the chief justice of the trial court. Official interpreters shall hold their positions at the pleasure of said department chief justice and shall render such additional services as said chief justice may require. Said department chief justice shall forthwith discharge any such official interpreter who shall be found by him to have requested or received, directly or indirectly, any gratuity, bonus or fee in connection with any criminal or civil case pending or in course of preparation for presentation to any court. Other official interpreters, or a telephone-based interpretation service, may be employed when the services of the official court interpreter are not available.