Why could a small mistake in formal words cause someone to lose a case under legis actiones?

Under the legis actiones system of Roman legal procedure, the preliminary stage of a lawsuit was governed by extremely rigid and formal requirements. Both the parties and the magistrate were required to recite specific, set forms of words to initiate or conduct the proceedings.12

This procedure was so strictly formal that even the slightest deviation or mistake in the required wording could result in a plaintiff losing their case entirely. Because the system relied on these precise oral formulas to define the legal issue, any error was viewed as a failure to properly establish the claim, leaving the magistrate unable to proceed. This emphasis on exact verbal compliance reflected the early nature of Roman law, where legal actions were tied to specific, ritualized expressions rather than the more flexible, written instructions that characterized the later formulary system.123