No, you're not in a position to. You'd have to kidnap Edge and force him to play his entire repertoire in front of a panel of qualified judges. Even that would not provide certain proof, though, since he might deliberately not play up to standard under those conditions, or he might be too agitated to play well. The judges might be prejudiced also.

I'm afraid we can't do better than hazard opinions about Ege's ability to play guitar well.

The same is true of many court decisions. The papers scream that so-and-so has been "found guilty!" or "found not guilty!" as if that was all there was to it, the final word, and all the proof necessary, but it's still often as not merely the opinion of a judge or a jury, and they might be wrong. They often have been wrong in the past.

Most of what people believe is simply their opinion.

To say that they disbelieve is also their opinion.

They almost never have undeniable proof to back it up.