"...a great deal of experience" from an unknown person is still very subjective. As has been debated in other threads recently, experience presented without knowledge of the source can be problematic. I am aquainted with a gentleman that can show you a resume with all kinds of experience and a ?Level III? (wink, wink) from a suspect source (not ASNT). I have witnessed him having trouble setting up to scan for laminations in plate, let alone conduct a competent UT weld inspection. Trouble is UT is one of those practices that unless you know what you are looking at, you can be fooled into thinking that the person is doing a fine job. Early in my career, my employer sent me to Krautkramer I and II school. He could have taught me himself, but he told me he was sending me for several reasons. One of the main reasons was he wanted me to have a very sound (no pun intended) base of knowledge because he did not expect me to be performing UT for the rest of my career. He expected me to be supervising someone else performing the inspection and to know whether they were doing a good job. I never forgot that and I have not wasted his money.
I think having someone you trust to supervise the person for a period of time would be valuable. It could be a Level III or it could be an aquaintance in the NDE field you trust and who you can compensate for his services. I had a layoff of almost a decade between assignments as a UT Level II. When my current employer wanted me to put my UT hat back on, I took several months to research current technology and equipment. Once I got my equipment and got pretty proficient setting it up and using it, I spent several sessions going to another local company where a friend that I trusted "looked over my shoulder" to see if I was doing a good job. He presented me some welds that he had already scanned in his shop and let me look for discontinuities. I told him to be blatently honest if I was not doing a good job, which he certainly was. Another inspector friend, who I greatly respect, has been into our shop to perform 3rd party verification inspections after me also. I have called him for advise several times over the years. So far he has only "busted" me one time and it was a marginal but valid call. Found my friends oversite was most valuable. Translate that to doing the same for an unknown candidate and that should become invaluable peace knowing your UT II is doing a competent job. I sure don't want any weld I accept to be found unacceptable once I put my name on it. The cost of rejections and repairs in the field, or worse, a failure of a weld in the field is too great to take a chance on.
I agree that an ACCP certified personnel should be a better risk when considering a candidate.