Here is a report of a Texas case which raises a novel argument:  In a bench trial is it necessary to present expert evidence of legal malpractice?  The argument is that evidence of a deviation from good and accepted practice must be shown to a jury, whose knoweldge generaly is insufficient for them to decide without expert testimony.  A judge who is finding the facts is in  a different situation, and it is often said that expert testmony on legal issues may not be presented to a judge. 

As an example, in a legal malpractice case arising from a non-filed appeal, it is the court’s decision, not a jury’s whether there would have been a different outcome.  Expert testimony on that aspect of the case is not permitted.

Is this the same argument?  In Texas, the answer was no.  "In Abdelhak v. Farney, plaintiff brought claims of legal malpractice and violations of the Texas Deceptive Trade Practices Act against his former trial attorney. No. 04-07-00121-CV, 2007 WL 4180133, at *1 (Tex. App.—San Antonio Nov. 28, 2007, no pet. h.) (mem. op.). Plaintiff alleged the defendant lawyer committed malpractice by failing to call certain witnesses, elicit certain testimony, and thoroughly conduct a cross-examination, but plaintiff failed to designate an expert witness prior to the designation deadline. Plaintiff sought leave to make a late designation and argued that his claims did not require expert testimony, but the trial court granted summary judgment. The San Antonio court affirmed. Id. at *4-5.

It is well-established that expert testimony is required to prove causation in legal malpractice cases arising from alleged trial errors because "the wisdom and consequences of these kinds of tactical choices" are beyond the knowledge of most jurors. Id. at *4 (quoting Alexander v. Turtur & Assocs., 146 S.W.3d 113, 119-20 (Tex 2004)). But this case had been set for a bench trial. The plaintiff argued that expert testimony should not be required in bench trials, because the lawyer’s negligence and the result of that negligence should be more obvious to a judge with legal training and experience. Noting that plaintiff had not provided any authority to support this argument, and observing that such a distinction would require a subjective determination of the particular trier of fact’s knowledge, the San Antonio court declined to modify the expert testimony requirement in the case of bench trials. "