A federal judge in Brooklyn has ruled that the conflicts of an individual lawyer should not be imputed to a firm he joined for only five months and where he worked in a separate office from the other lawyers in his practice group.

First Unum Insurance Co., the defendant in a suit claiming the company improperly denied long-term disability coverage, moved to disqualify the plaintiff’s firm, Binder & Binder, on the grounds that Peter J. Heck, a former lawyer at the firm, had represented Unum several times while working at another firm.