Hilgraeve Corporation v. McAfee Associates, Inc.

Hilgraeve Corporation (plaintiff) held a patent over an invention entitled “In Transit Detection of Computer Virus with Safeguard” (the ’776 patent). The claimed invention scanned data with potential viruses as the data was being transferred and before storage of it on a destination storage medium; if the program detected signs of a virus during the scan, the program would automatically block storage. During prosecution of the ’776 patent, the patent examiner had initially rejected all the claims. In response and to procure the patent, Hilgraeve added claim 18 and, later, amended claim 1. Claims 1 and 18 specified that the invention automatically inhibited, i.e., stopped, storage of the data if certain conditions were met, and claim 1 additionally stated that the transferred digital data was screened “prior to storage” on the destination storage medium. Hilgraeve sued McAfee Associates, Inc. (McAfee) (defendant) for patent infringement based on McAfee’s product VirusScan. On summary judgment, Hilgraeve argued that VirusScan infringed the patent literally or under the doctrine of equivalents. McAfee asserted that it was entitled to a ruling of noninfringement because VirusScan did not screen for viruses prior to storage of data. According to McAfee’s expert, VirusScan first stored digital data and then screened for viruses. Hilgraeve’s expert disputed the tests used by McAfee’s expert, and neither expert clearly addressed the extent of VirusScan’s inhibition or manipulation of data with respect to the operating system. The trial court ruled that Hilgraeve was estopped from arguing infringement under the doctrine of equivalents and granted summary judgment of noninfringement to McAfee. Hilgraeve appealed.