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It would be next to impossible, you would have to be able to prove that every last molecule went to legitimate research of some sort, and any evidence that it was used otherwise (like posts on an Internet drug forum) would probably get you charged regardless
You don't have to worry about this, you are innocent until proven guilty (in the US at least). They would have to prove you have consumed/intend to consume them.
It wouldnt be hard to prove consumption depending on how the chemical is stored (IE: next to razor blades, mirrors, other typical 'powder paraphenelia)' and if youre caught with a straw that has the chem residue in it, youre as good as fucked i would imagine..