Having worked both "for" and "against" the FDA wrt clinical trials and litigation therein (I was an employed by the manufacturer of a particular drug, then worked at the same company - doing the opposite job, practically - as a contractor. I've also worked for a CRO), I can pretty much guarantee you that the patient signs an informed consent form and the risks are verbally outlined, and with most CROs/investigator sites, there's ANOTHER form the patient signs separately to confirm that the risks have been outlined and the patient understands.
Incidentally if we don't get those forms, the patient is rejected for the trial period - even if they fit every other criteria.
I agree with emc - claiming ignorance is just not going to be viable in the OP's scenario.