Should a plaintiff always need an expert witness in a malpractice case?

Because the practice of law is considered to be a profession, and a profession is defined, among other things by the fact that it requires special knowledge, education and training, courts usually require that plaintiffs in malpractice actions provide an expert witness to support their arguments as to duty and breach to the jury.  But what if there is no jury?  What if the case is going to be a bench trial?  Should a plaintiff be required to have an expert to explain to the judge what the standard of care of the profession is?  Or can we assume that the judge - obviously a lawyer himself or herself - knows the law that applies to the practice of the profession they belong to?

In a recent case in Delaware (Cannon v. Poliquin), the court decide no help from an expert is needed.  Go here for a short summary.