Fed Court: First Amendment Protects Engineers Expert Testimony Without a License

This seems like the right answer. An "expert" should be someone whose field of expertise is in the subject being presented to the court. The opposing counsel can (and should) challenge it when appropriate. A PhD in medicine or PE cert is a pretty good bona-fides to presenting a person as an expert to the court, but it doesn't mean that some amateur naturalist whose spent 20 years studying the population of butterflies in the Sierra foothills couldn't be considered an expert in that specific topic of discussion either. Just that their scope might be more limited than the Phd.

California law doesn't seem to make the sort of distinction either, for example:

720. (a) A person is qualified to testify as an expert if he has special knowledge, skill, experience, training, or education sufficient to qualify him as an expert on the subject to which his testimony relates. Against the objection of a party, such special knowledge, skill, experience, training, or education must be shown before the witness may testify as an expert. (b) A witness' special knowledge, skill, experience, training, or education may be shown by any otherwise admissible evidence, including his own testimony.

721. (a) Subject to subdivision (b), a witness testifying as an expert may be cross-examined to the same extent as any other witness and, in addition, may be fully cross-examined as to (1) his or her qualifications, (2) the subject to which his or her expert testimony relates, and (3) the matter upon which his or her opinion is based and the reasons for his or her opinion.

The point of this case was that an expert can testify without licensure, not that they can misrepresent themselves to the public.

Eh it really depends on the context. When I got my EE degree I was told getting your PE only really mattered if you worked on the power grid or similar. It wasn’t that you were less of an engineer or an expert without it but that 1) you didn’t need the legal ability to sign design documents most of the time 2) even if you took the exam to become an FE, the odds of you working under a licensed PE to get the requisite hours was so small it wasn’t worth the effort to take the FE exam.

If the case involved a field where a PE is standard, the expert witness should 100% have that license. However that’s a small number of sub-fields in practice and doesn’t necessarily correlate with practical experience.

You can be an expert of engineering and perform engineering work without being acknowledged or licensed by some authority. A country can have engineers before they even have a PE org or guild or system, after all.

Oh, absolutely! And let's not forget, you're not a real musician unless you've got a Musician's License. All those unlicensed folks playing in orchestras and bands are just faking it, obviously.

Indeed. If you're not building medieval siege works then you too aren't a real engineer.