Alperin Technical Pty Ltd & Anor v ACI Australia Limited

This matter came before the High Court of Australia on an application for special leave to appeal. The applicants, Alperin Technical Pty Ltd and another party, sought leave to appeal against a decision concerning a commercial agreement for a pilot plant to manufacture a building product. The respondent, ACI Australia Limited, sought to terminate the agreement on the basis that a condition precedent had not been met, specifically relating to the completion of certain tests by 31 October 1989.

The core legal issues before the court concerned the interpretation of the commercial agreement. Specifically, the court was required to determine whether the agreement mandated the completion of not only the trials by the end of October 1989, but also the testing of the product itself by that date. Furthermore, the court had to consider whether the "testing process" encompassed compliance with technical specifications for the product's properties, or if it extended to other, broader requirements. A related issue was the circumstances in which extrinsic material may be used to aid the interpretation of a commercial agreement, and the principles governing estoppel by convention.

The applicants argued that the judgments below adopted different approaches to contractual interpretation. One judge, Mr Justice Tadgell, focused on the agreement's text and internal context, while Mr Justice Murphy, in contrast, appeared to consider the parties' commercial intentions and realities before examining the contractual language. The applicants contended that this divergence highlighted a significant debate regarding the admissibility and use of extrinsic evidence in contract construction, referencing principles discussed in *Codelfa* and academic commentary on the topic. The applicants submitted that the court should determine the circumstances in which extrinsic evidence might be used to interpret a contract.