2.11 EXPERT OPINION
Some witnesses, because of education or experience, are permitted to state opinions and the reasons for those opinions.
Opinion testimony should be judged just like any other testimony. You may accept it or reject it, and give it as much weight as you think it deserves, considering the witness’s education and experience, the reasons given for the opinion, and all the other evidence in the case.
See Fed. R. Evid. 602, 701–05.