The short answer to the question of when an expert is necessary in legal malpractice is "most of the time."  Here in this case, Whalen v DeGraff, Foy, Conway, Holt-Harris & Mealey ,2008 NY Slip Op 06342 [53 AD3d 912] ,July 17, 2008 ,Appellate Division, Third Department  we see the slightly longer answer on a motion for summary judgment [same rule would obtain for trial]:
 

"While plaintiff would ordinarily be required to submit an affidavit of an expert setting forth the applicable standard of care in order to obtain summary judgment in her favor (see Alvarez v Prospect Hosp., 68 NY2d 320, 324 [1986]; Zuckerman v City of New York, 49 NY2d 557, 562 [1980]), no such affidavit is necessary here because it is undisputed that defendant knew of the deadline for filing the notice of claim and took no steps whatsoever to even inquire as to the status of that filing between February 1996 and January 1998 (see Shapiro v Butler, 273 AD2d 657, 658 [2000]; S & D Petroleum Co. v Tamsett, 144 AD2d 849, 850 [1988]). Thus, plaintiff’s motion for summary judgment should have been granted to the extent of awarding her judgment as a matter of law with respect to defendant’s negligence in failing to supervise Bailey. In light of this determination, we find that Supreme Court properly denied defendant’s motion for summary judgment dismissing the complaint (see Zuckerman v City of New York, 49 NY2d at 562; Guiles v Simser, 35 AD3d 1054, 1055 [2006]). "