It will probably be neural science that will perfect lie detection. It all begins in the brain.Even so it will still only prove you believe you are telling the truth, in other words, you believe your memory of an event is true. It is still not evidence for the actual claimed event.
True for finding the cosmic consciousness but not true in communicating with my wife. That confirmation would clinch it in my mind but if others are not convinced by it there in nothing I can do.
If you firmly believe something (because it really happened, or because you are crazy, or because someone you really trust says it happened, or whatever reason) any brain test, no matter how sophisticated, will show that you think it is true
. A lie detector won't help if the person does not know they are "lying". That is why lie detectors don't work on sociopaths and con artists. They are so convinced of their own reality that they are not actually lying.
As for you and your wife, there are cases of shared delusions. You can find accounts of groups of people saying they saw an alien spaceship, or bigfoot or the Virgen de la Guadeloupe, or a unicorn. Does not mean that those things really exist. Just means people brains can work in tandem to produce false positives.