Here is a SDNY case in which plaintiffs sued for legal malpractice, and lost the bench trial and the appeal.  The decision does not spell out what was ambiguous about the retainer agreement, but both the bench and the appeal court determined that this "engagement" letter was insufficient to spell out an attorney-client relationship.

LATIN AMERICA FINANCE GROUP, INC. and WILLIAM VAN DIEPEN, Plaintiffs-Appellants, -v.- CARLOS PAREJA and PAREJA Y ASOCIADOS, Defendants-Appellees. 06-3888-cv
UNITED STATES COURT OF APPEALS FOR THE SECOND CIRCUIT

2008 U.S. App. LEXIS 4048

Interesting too was the trial court’s inclusion and exclusion of expert testimony.  Apparently for defendant, it permitted the testimony.  It excluded for plaintiff because the expert testimony consisted of "fact finding, the application of law to facts, and the drawing of conclusions as a result of the application of law to facts. "  This problem exists at all times, but is especially difficult in a bench trial, where the fact finder is, after all, a judge who neither needs, nor wants, application of law to facts.