To establish legal malpractice under New Hampshire law, under either a contract or tort theory, a plaintiff must prove (1) the existence of an attorney-client relationship, "which placed a duty upon the attorney to exercise reasonable professional care, skill and knowledge in providing legal services to that client;" (2) a breach of that duty; and (3) "resultant harm legally caused by that breach." Yager v. Clauson , 166 N.H. 570, 572–73, 101 A.3d 6, 9 (2014)(citing Estate of Sicotte v. Lubin & Meyer, P.C. , 157 N.H. 670, 674, 959 A.2d 236, 240 (2008). "Whether [an] attorney has breached the applicable standard of care in representing the client is a question of fact to be determined through expert testimony and usually cannot be decided as a matter of law."
Thus, "[t]o establish legal malpractice a plaintiff must prove: (1) that an attorney-client relationship existed, which placed a duty upon the attorney to exercise reasonable professional care, skill and knowledge in providing legal services to that client; (2) a breach of that duty; and (3) resultant harm legally caused by that breach." Yager v. Clauson, 166 N.H. 570, 572-73, 101 A.3d 6 (2014) (quotation omitted). As the foregoing implies, an action for legal malpractice "is a claim ... for liability ‘unique to and arising out of the rendition of professional services.’ "