So his opinion on whether or not Dr. D was qualified in her expert opinion is based solely on what the Defence team has told him about her testimony.
Bet JW didn't tell him about the part where Dr. DeMarte said "those scales can't be just read and interpreted that way" and JW replied "well, let's do it anyway".
IMO, as long as he hasn't heard or read her entire testimony and only relies on the (at times mis-)representation the Defence team gives, he has no place testifying about it in the first place.
Gosh, this whole testimony makes me angry.