Proving mistakes by an attorney is really the least difficult aspect of litigating a legal malpractice case.  Technical aspects of the action, such as timelyness, pleading, proximate cause, and privity often overshadow a simple analysis of mistakes.

Here is a case from Michigan in which the attorney filed a divorce action in the wrong county!  Howver, plaintiff could not demonstrate damages.  They tried gamely to show that the plaintniff had to rent an apartment in the next county, and had to spend money to move around.  Result?  No damages.