It is policy of this state that all qualified citizens have an obligation to serve on petit juries or grand juries when summoned by the courts of this state, unless excused. Every person eighteen (18) years of age, being a citizen of the United States, and a resident of this state, and of the county in which the person may be summoned for jury service for a period of twelve (12) months next preceding the date of the summons, is legally qualified to act as a grand or petit juror, if not otherwise incompetent under the express provisions of this title.