That could be difficult. It's difficult to get the CoS to pin down exactly what it is that the e-meter is supposed to be measuring ("mental energy"), so it's impossible to tell whether it's measuring it or not. Of course it's possible to show that it _also_ measures resistance when used in a certain way, but no doubt the CoS would say that it only works when used properly.

How could they do an experiment to show conclusively that whatever vague claims the CoS makes about the e-meter are false?