Each state can make its own choice about whether to license (or certify) polygraph examiners. Some states have no rules whatsoever, while other states are very strict about internships, procedures, etc.
Texas used to be strict. But it did away with its licensing requirement in 2021.
I was the last Texas in-state polygraph examiner licensee. That means that I had to go through the rigorous process of training, internship, reporting, etc. Make sure that your polygraph examiner is or was licensed in Texas (or your state if applicable) before the rules changed, and/or holds an active license in appropriate states. Both scenarios apply successfully to me, thus I can lawfully conduct a polygraph exam in well over half the states.
I’m currently licensed in Louisiana, North Dakota, and Tennessee. As such I have direct polygraph capabilities in those home states, reciprocal in 4 other states, and can conduct polygraphs in all 24 other states not requiring a license.
If your polygraph issue is related to sexually-based topics, it is also great to have someone who is trained specifically in sexually-related polygraph work. In Texas, this would be by attending the Joint Polygraph Committee on Offender Testing's initial training and continuing education.