When a transaction has been reduced to writing, either by requirement of law or by agreement of the parties, the writing becomes the exclusive memorial thereof, and no extrinsic evidence is admissible, either to prove the transaction independently or to contradict, vary, add to or subtract from, the terms of the document, though the contents of such a document may be proved either by primary or secondary evidence.
This rule is based on two grounds: (1) that to admit inferior evidence when the law requires superior evidence would be to nullify the law; and (2) that when the parties have deliberately put their agreement into writing, it is conclusively presumed between themselves that they intended the writing should be placed beyond the reach of future controversy, bad faith or treacherous memory.
All parole testimony of conversation held between parties, or declarations made by either of them, whether before, or after, or at the time of a contract, will be rejected, because such evidence would tend to substitute a new and different contract for the one actually agreed upon.
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ADVERTISEMENTS:
This section excludes the evidence of oral agreements, and it applies to cases where the terms of contracts, grants or other dispositions of property have been proved by the production of the relevant documents themselves under S. 91; in other words, it is after the document has been produced to prove its terms under S. 91, that the provisions of S. 92 come into operation for the purpose of excluding evidence of any oral agreement or statement, for the purpose of contradicting, varying, adding to or subtracting from its terms. The application of this rule is limited to cases between parties to the instrument or their representatives in interest.