In this Lexology report from Hinshaw an attorney was covered by the initial insurance even after leaving the firm, even for work later performed:

"Kimberly A. Jolley, et al. v. John J. Marquess, et al., ___A.2d___, 2007 WL 1518114 (N.J.Super.A.D.)

Addressing a question of first impression, the Appellate Division of the New Jersey Superior Court held that a malpractice insurance policy’s definition of “insured” – which included a former partner “while acting solely in a professional capacity on behalf of” the partner’s former firm – required the insurer to defend and indemnify for work the lawyer did both before and after he had left the firm. The decision has important things to say not only about the scope of malpractice coverage but also about the importance for attorneys and insurers alike of proper transfer of client matters when a lawyer leaves a firm. "