I said about metallic signature which is not a chance when you measure an ectoplasm. If it doesnt have metallic it wont ever have, but I get the point. Thanks!

In the rules, it mentions that you cannot guess the Mejai, which is fair.

However, is a lack of evidence enough to consider it confirmed?

For example, both Dekan and Necreph got Destroy Objects, Projects Voice and Eletronic Disturbance, and while both have Radioactivity, only Necreph has Metallic Signature.

If I find an ectoplasm after getting the object, voice and eletronic, and test it for Metallic Signature, if it doesnt react is it enough for me to prove thats Dekan or I do need another evidence?