There are a few situations in legal malpractice where an expert is not needed for plaintiff.  An expert is needed, in general, when the subject matter is unknown or too complicated for lay jurors to understand or determine, and they require explanation by a person who is professionally or educationally acquainted with the specialized field. 

Whether an act by the target attorney was a departure from the good and applicable standards of attorney practice is almost always the province of an attorney-expert.  The few exceptions are only the most basic of mistakes, such as a forgotten statute of limitations.

Here, in Tran Han Ho v Brackley   2010 NY Slip Op 00575   Decided on January 28, 2010   Appellate Division, First Department  we see two mistakes:  the failure to offer an expert, and an attempt to offer an expert opinion on sur-reply.  We envision plaintiff’s attorney reading defendant”s reply with dread, seeing [hypothetically] the argument that no expert opinion has been submitted and that summary judgment must issue.
 

"The motion court properly refused to consider the sur reply affirmation of plaintiffs’ legal expert presented to the court after the motion had been fully submitted (see Foitl v G.A.F. Corp., 64 NY2d 911 [1985]). Absent an expert’s affidavit, and given claims that, as pleaded, raise issues of professional standards and causation beyond the ordinary experience of persons who are not lawyers, summary judgment was properly granted (see Ehlinger v Ruberti, Girvin & Ferlazzo, 304 AD2d 925, 926 [2003]; cf. Butler v Brown, 180 AD2d 406, 407 [1992], lv denied 80 NY2d 751 [1992], citing S & D Petroleum Co. v Tamsett, 144 AD2d 849, 850 [1988])."