In Kassis v. Teacher's Ins. and Ann. Assoc. (93 NY2d 611, 717 N.E.2d 674, 695 N.Y.S.2d 515 ) an attorney who conducted some depositions and had appeared for a firm client in a mediation, later joined a firm that was representing that client's adverse party on the same pending matter.
The Court of Appeals concluded that given these facts, the attorney and firm to be disqualified could not rebut the "presumption of shared confidences" and that a screen to prevent the sharing of any acquired confidences with the new firm would be "inconsequential."
The Court disqualified the attorney and firm in Kassis even though the attorney avowed that he had only read small parts of the firm's case file for purposes of the depositions he conducted, and that an effective screen had been erected since joining his current firm.
The Court also reaffirmed the important roles of a presumption of disqualification, noting that it "reinforces an attorney's ethical obligation to avoid the appearance of impropriety," it "protects client confidences from misuse," and it "frees the former client from any anxiety that matters disclosed to an attorney will subsequently be used against it in related litigation." (Id. at 616).