Comment by ibejoeb
1 day ago
It's not about his testimony on this particular issue. In fact, it does not appear that he has given any. It's about his qualifications to potentially testify. Even so, in American courts (in which he has previously qualified,) the qualification process is adversarial and involves both direct and cross-examination, so if he wasn't actually qualified, the opposing party would certainly argue as much.
The reality of expert witnesses is not that they are authoritative sources outside the courtroom, but witnesses for one party. It's a job - sometimes for people who didn't find much success in their field - and they are paid by the party that calls them to testify.
Everything in a US courtroom is adversarial; every witness is cross-examined and their credibility can be questioned.