Defense attorneys have lost a bid to put an expert on memory and perception on the witness stand in the trial of a woman accused of handing a loaded gun to a teenage relative and telling her to shoot another girl.In a written opinion last week, U.S. District Judge Amy St. Eve held that such testimony is inadmissible in Vandetta Redwood’s trial on federal firearms charges.An expert, St. Eve wrote, would trample on ground that belongs to jurors.Jurors do not need someone to explain, for example, that a witness&rsquo …