The term ‘consulting expert’ is used to refer an expert, who though retained by a party, is not expected to be called as a witness at trial. A consulting expert is also termed nontestifying expert. A consulting expert’s opinions are generally exempt from the scope of discovery.
However, a consulting expert can assist the defense counsel to find areas the expert can testify about that are helpful to the defense. And then the counsel can minimize anything damaging said by the prosecution's expert on direct. [Eze v. Senkowski, 321 F.3d 110, 129 (2d Cir. 2003)].