Privity of contract is an essential in legal malpractice litigation.  One may not sue the opponent’s attorney; only one’s own.  What makes for privity of contract?  As all know, no writing is necessary to create a contract.  So, can there be privity of contract without a retainer agreement.  Putting aside Rule 137 questions about the attorney’s obligation to provide a writing, in Denise Terio,  v Lance Roger Spodek, Reich Reich & Reich, P.C., 2008-03594, 2008-04435;  SUPREME COURT OF NEW YORK, APPELLATE DIVISION, SECOND DEPARTMENT; 2009 NY Slip Op 4412; 2009 N.Y. App. Div. LEXIS 4411June 2, 2009, Decided we see a short answer:
 

"To recover damages for legal malpractice, a plaintiff [**4] must prove, inter alia, the existence of an attorney-client relationship (see Velasquez v Katz, 42 AD3d 566, 567, 840 N.Y.S.2d 410; Moran v Hurst, 32 AD3d 909, 822 N.Y.S.2d 564; Wei Cheng Chang v Pi, 288 AD2d 378, 380, 733 N.Y.S.2d 471; Volpe v Canfield, 237 AD2d 282, 283, 654 N.Y.S.2d 160). While a plaintiff’s unilateral belief does not confer upon him or her the status of client (see Volpe v Canfield, 237 AD2d at 283), an attorney-client relationship may exist in the absence of a formal retainer agreement (see e.g. Swalg Dev. Corp. v Gaines, 274 AD2d 385, 386, 710 N.Y.S.2d 619). To establish an attorney-client relationship there must be an explicit undertaking to perform a specific task (see Wei Cheng Chang v Pi, 288 AD2d 378, 733 N.Y.S.2d 471; Volpe v Canfield, 237 AD2d at 283)."