Pleading in legal malpractice can be tricky.  Here is a recent New York case Shefa Unlimited, Inc., et al. respondents, v Amsterdam & Lewinter, 2006-10191 SUPREME COURT OF NEW YORK, APPELLATE DIVISION, SECOND DEPARTMENT 2008 NY Slip Op 1937; March 4, 2008, Decided, which reports the unsuccessful attempt to add new allegations against a law firm in a "relation back" setting.

"In the proposed second amended complaint, the plaintiffs sought, in effect, to assert a new cause of action to recover damages for legal malpractice. However, that cause of action was time-barred (see CPLR 214[6]). Moreover, the original complaint did not give the appellants notice [*2]of the alleged transactions, occurrences, or series of transactions and occurrences that formed the basis for the new cause of action (see CPLR 203[f]). Under these circumstances, where the proposed pleading was not a "mere extension" of the allegations in the original complaint, and thus, did not "relate back" to that pleading, the Supreme Court improvidently exercised its discretion in permitting the amendment (Krioutchkova v Gaad Realty Corp., 28 AD3d 427, 428). Indeed, although leave to amend a pleading is to be freely granted, leave should be denied where, as here, the opponent would suffer prejudice or surprise resulting directly from the delay in seeking leave, or the proposed amendment is palpably insufficient or patently devoid of merit (see CPLR 3025[b]; Nissenbaum v Ferazzoli, 171 AD2d 654, 655; Barnes v County of Nassau, 108 AD2d 50, 52). "