Your lab blows up...
If the lab blows up with a signature brimstone stench and evil cackling, sure. Otherwise, it's a lab accident.
... Although accusations of tainted vis, valid or not, could easily fly after any botch. There's a plot point.
I'd have to reread the section. I think prava it just blows up. I'd also like to think that magi know if they are experimenting or not. If the lab blows while not experimenting...
Then again someone infernal working with infernal Vis can blame such happenings on experimentation.
I should think you can use Lore skills to identify vis. It's probably not easy, but if you can use Lore skills to identify and process items of virtue, you could do the same with plain old raw vis (otherwise, few hedgies would ever identify vis). Someone with Infernal Lore should be able to identify Infernal Vis with a good enough roll, and possibly identify the extent of the taint. How good a roll you'd need for this I cannot guess.
"You study demonic lore? Clearly, this is a sign of evil intent! You shall be Marched!"
No, I imagine that doesn't actually happen. Preparation is, after all, the best defense magi have. (And, for that matter, the best offense. The latter is sort of a double-edged sword for this consideration, though.)
Knowledge is the best way of avoiding the Infernal, after all. Most of them have sovereign wards that makes them avoid you or unable to attack you. Smart authors would title their books of Infernal Lore with useful titles like "Avoiding Eternal Damnation in 4 Easy Steps" or "Why Demons are the Enemy of the Order of Hermes" or "How to Stop Infernalists In Their Tracks".
Instead, you get dummies titling stuff with "The Dark Arts" or "How the Infernal Can Make You All Powerful".
What he says: "Why, I didn't write that! It must have been a demon, using my name to frame me for dabbling in Infernalism!"
What everyone knows really happened: "Bwahaha, I shall bring darkness into this world for my dark overlords!"
...
What actually happened: "This human has great story potential! I should don the glamour of a demon... Or maybe even an identical twin of him!... and write a book using his name praising the dark arts! Oh, this should yield such precious panic! Delightful!"
Faeries are the real evil in this world, not demons. 
Meh everyone knows that real demons detect as Divine and have powerful illusions or mind control to spoof Sense Unholy.
Demons probably spend all there time writing books that seem nice and friendly on the outside, but actually corrupt your personality or abilities.
That''s true, and I think you're right there. Maybe only Infernal Lore people know how it works, but everybody should at least know it exists. I agree with you.