>witnesses for one party

>every witness is cross-examined and their credibility can be questioned

I think we're talking about different stages. The determination of his qualifications happens before he can be a witness for one party. I'm talking about voir dire. Before we even get him on the stand, there's a separate hearing to determine if he can even be an expert witness, and the opposing party can challenge.

Anyway, there is no ongoing action that I can find. It's only just come into effect, so that's to be expected. As far as an authoritative source for the argument: the person we're discussing is actually the author.