Evidence
Parol Evidence (Evidence Context)
Definition
In the evidence context, the parol evidence rule is a substantive rule of contract law that operates as an evidentiary bar, preventing the introduction of prior or contemporaneous oral or written agreements to contradict a fully integrated written contract. While sometimes discussed in evidence courses, it is technically a rule of substantive law rather than a rule of evidence. Courts evaluate whether the writing was intended as a complete and final expression of the agreement (integration) before applying the rule.
Example
A written lease states rent is $1,000 per month. The tenant cannot introduce testimony of an earlier oral agreement that rent would be $800 if the lease is fully integrated.