Computer Associates International, Inc. v. Altai, Inc., 982 F.2d 693 (2d Cir. 1992) is a leading decision from the United States Court of Appeals for the Second Circuit on how to establish copyright infringement for software. The Court overturned the previous test for infringement set by Whelan v. Jaslow. The United States Court of Appeals for the Second Circuit is a federal court with appellate jurisdiction over the district courts in the following districts: District of Connecticut Northern, Southern, Eastern, and Western Districts of New York District of Vermont The Second Circuit hears argument at the Thurgood Marshall U... Copyright infringement (or copyright violation) is the unauthorized use of material that is protected by intellectual property rights law particularly the copyright in a manner that violates one of the original copyright owners exclusive rights, such as the right to reproduce or perform the copyrighted work, or to make...

Altai hired an ex-employee of Computer Associates. In the course of his work at Altai the employee used code owned by Computer Associates. During a lawsuit brought by Computer Associates, it was found that the code written by employee consisted of 30% of code taken from his previous employer. Altai had the program rewritten by programmers who had never seen the infringing code (a clean room rewrite). Computer Associates sued Altai again on the basis that the second version of the code infringed their original code. CA, Inc. ... Clean room design is the method of copying a design by reverse engineering and then recreating it without infringing any of the copyrights and trade secrets associated with the original design. ...

The Court held that there was no infringement in the second version. A new test for substantial similarity, known as the "abstraction/filtration/comparison" test, was developed that was largely based on the reasoning in Nichols v. Universal Pictures Co.. The filtration test first examines the allegedly infringed program and excludes from consideration design elements made for efficiency, elements dictated by external factors, and elements taken from the public domain. Anything left over is protectable. In this case, Altai successfully defended against the copyright claim because everything CA claimed was filtered out. Nichols v. ...

The case also established that a lay observer's opinion of infringement is not relevant to complicated subjects like computer software.

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