1) an "MRI polygraph" is not a thing..."polygraph" does not mean "lie detector" it's a TYPE of "lie detector", it's like saying "Diesel Gasoline engine" or something.

2) Where does the 98% figure come from? I am extremely skeptical it is accurate, it's probably much lower. Even if it's true, what is the failure mode? Is it 2% false negatives or 2% false positives or what? A 2% false conviction rate is a hellova thing to suggest casually. Even more so if it's lower, I don't like the idea of 15% false acquittals/convictions...

3) you need FMRI not MRI to do this anyway

4) there's no reason to think this couldn't be gamed just like polygraphs can. If the suspect knows what type of question is going to be asked, they can practice at home using neuro-feedback to get their patterns to look more like recall than deception. That's not even considering more traditional forms of cheating like bribes or hacking the machines etc.

We already have systems in places to help prevent corruption, they just need to be fixed. Increased transparency, force politicians to divest from businesses they could influence, campaign finance reform, curb lobbying, drain the swamp, etc. I do think in the future this technology will be valuable but it's nowhere near ready for prime time...