> No helium, no fusion. Excess energy is a red herring.
I'm not sure whether to vote you up or down. Yes, a physical by-product is the best determinant of a nuclear reaction, but the whole point of this endeavor is the excess energy!
Not if it's being generated from some prosaic source, like (just shooting from the hip here) oxidizing palladium for example. And not if it's not reliably reproducible.
It's very simple to tell if there's fusion going on: if there's fusion, there will be helium. No helium, no fusion. Excess energy is a red herring.