I don't know what 'TFA' is, but you say that it says experts should be paid, so I don't understand what your argument is here.

The second scenario you describe is clearly corrupt, but I don't see how paying a consultant for their time is the objectionable part; when you stack that against a DA on the take, a police force on the take, and a rich man fabricating evidence, that all seems like a larger problem to me than "the rich man can pay an expert to testify about their expertise", especially given that the testimony of the expert witness can be challenged.