517.091.  Trial by jury, when waived — jury trial, how granted — composition of jury. — 1.  In any case triable before a jury, a trial by jury shall be deemed waived unless written demand be filed not later than five days before the return date of summons or  the date set for trial, whichever is later.  For good cause shown, the judge may grant any party's request for jury trial.

  2.  A jury shall be composed of twelve qualified jurors, unless all parties agree on a lesser number, but not less than six, in which case the number of veniremen shall be reduced accordingly.  Three-fourths or more of any jury concurring may return a verdict.