The Missouri Constitution article 1, section 22 (a) provides that "the right of trial by jury as heretofore enjoyed shall remain inviolate ..."' The Missouri Supreme Court has interpreted this to mean that it does not extend or contract the right to trial by jury, but preserves the right as it existed at the time of the adoption of the constitution. In other words, since each of Missouri's four constitutions have similar provisions, the right is preserved as it existed in 1820, the date of adoption of Missouri's first constitution. At common law not all civil matters were tried before a jury. Issues in actions at law were triable by a jury as a matter of right while issues in suits in equity were not. Equitable issues could, however, be submitted to an advisory jury at the discretion of the chancellor. This distinction between law and equity has been perpetuated by constitutional provision and is today the most important remaining difference between the two systems. The mandate of the constitution provides a test which is primarily historical in that it requires the right of trial by jury to exist today as it did at common law in 1820. One exception to the provision that suits at law are triable by a jury as a matter of right in Missouri is the sanctioning of the pre-existing practice of appointing a referee to determine long and complicated factual issues in a suit at law. The state constitutional right to a jury trial does not extend to newly created remedies which did not exist at common law. This means that the legislature has authority to determine if a new remedy carries with it the right to a trial by jury. If the legislature fails to state how a new remedy is to be tried, it is for the courts to apply the historical test and determine whether the remedy is of legal or equitable cognizance. It has also been held that the legislature has the power to provide for a jury trial in civil cases where it previously did not exist as a constitutional right. A few states have construed their constitutions to guarantee the right of a non-jury trial in equitable matters. The right to a jury trial may be waived and both the legislature and the courts have the power to set forth reasonable regulations concerning when a jury trial may be demanded, the form of the demand, and what constitutes waiver.
Thomas Jean O'Neil,
Law or Equity: The Right to Trial by Jury in a Civil Action,
35 Mo. L. Rev.
Available at: https://scholarship.law.missouri.edu/mlr/vol35/iss1/9