We think there is no more difficult case in litigation than a legal malpractice action arising from a medical malpractice case.  The issues of proximity and "but for" multiply and boggle the mind.  One needs a medical expert as well as a legal expert, and while having to prove the causation in a medical malpractice case, hypothetically is difficult anyway, moving on to prove the causation in the legal malpractice portion squares rather than doubles the effort.

In Palumbo v Dell ; 2010 NY Slip Op 03889 ; Decided on May 4, 2010 ; Appellate Division, Second Department we see an example. In a simple situation in which the note of issue was not timely filed, plaintiff loses the whole case for lack of a medical expert.  Note that suing the attorney who did not file the note of issue is practically impossible, as proximate cause now must be proven to the 4th power.
 

"An action dismissed pursuant to CPLR 3216 may be restored only if the plaintiff can demonstrate both a reasonable excuse for the default in complying with the 90-day notice and a meritorious cause of action (see Picot v City of New York, 50 AD3d 757; Sapir v Krause, Inc., 8 AD3d 356, 356-357; Lopez v Imperial Delivery Serv., 282 AD2d 190, 197). Here the plaintiff failed to demonstrate the merits of his legal malpractice action, which alleged that the defendants were negligent in failing to pursue a strict products liability claim against the manufacturer of a phacoemulsification unit utilized during the plaintiff’s cataract surgery. Notably, the record is devoid of any expert medical evidence establishing the merits of the products liability claim, and there is no other showing that the plaintiff would have succeeded on such a claim (see N.A. Kerson Co. v Shayne, Dachs, Weiss, Kolbrenner, Levy & Levine, 45 NY2d 730, 732; Matera v Catanzano, 161 AD2d 687, 688; see also Ideal Steel Supply Corp. v Beil, 55 AD3d 544; Payette v Rockefeller Univ., 220 AD2d 69, 74). Accordingly, the Supreme Court [*2]properly denied the plaintiff’s motion (see Mosberg v Elahi, 80 NY2d 941, 942; Serby v Long Is. Jewish Med, Ctr., 34 AD3d 441). "