A rule written by the courts, not the legislature
Missouri's pure comparative fault system traces back to a genuinely distinctive origin: Gustafson v. Benda, 661 S.W.2d 11 (Mo. banc 1983), in which the Missouri Supreme Court itself adopted the Uniform Comparative Fault Act "insofar as possible," abolishing the older doctrines of contributory negligence, last clear chance, and humanitarian negligence all at once. A dissenting judge called it "a giant legislative enactment by judicial fiat" — a genuinely sharp characterization of just how significant a shift this was, coming from the court rather than the General Assembly.
No bar, no matter how high your fault
Under this system, a claimant's damages are reduced by their own percentage of fault, but recovery is never barred entirely, regardless of how high that percentage climbs. A claimant found 90% at fault still recovers 10% of their total damages.
The legislature eventually caught up
It wasn't until July 1, 1987 that the Missouri Legislature formally codified comparative fault for product liability cases specifically and abolished contributory negligence in negligent tort cases by statute — four years after the Supreme Court had already made the underlying policy shift through Gustafson itself.
Worked example
Someone with $100,000 in damages, found 30% at fault, recovers $70,000. That same person, found 70% at fault, still recovers $30,000 — a genuinely meaningful difference from a modified comparative state, where crossing a 50% or 51% threshold would reduce that same claimant's recovery to zero.
A distinctive wrinkle: seat belt non-use
Missouri's seat belt law creates its own separate damages-mitigation argument, rather than functioning as a true comparative fault defense folded into the general fault percentage. This is a genuinely distinct legal mechanism worth understanding on its own terms rather than assuming it simply adds to a claimant's overall fault share.