Henry Kassis and North River Insurance Company (plaintiffs) retained the firm Weg and Myers to represent them in 1994 in an ongoing property damage lawsuit. Partner Joshua Mallin handled strategy and most discovery, while first-year associate Charles Arnold took five depositions, attended mediation and a site examination, and spoke regularly with the client. Arnold reviewed portions of the litigation file conducting depositions, but claimed he never read most documents in it. In 1997, Arnold lateralled to opposing counsel’s firm, Thurm and Heller. The firm warned Arnold that he would not be allowed to participate in the matter and imposed screening measures to prevent inadvertent disclosure of confidential information from his previous employment, including preventing Arnold from accessing the litigation file and involvement in any related discussions. Three days later, Mallin asked the court to disqualify Arnold’s entire new firm from representing the defendants. The trial court refused, finding Arnold had limited involvement in his prior employment. The appellate court found the screening measures adequate to prevent inadvertent disclosure of confidential client information. Plaintiffs appealed.