If you falsify a medical form, then the responsibility is yours and yours alone.
Somehow I'm guessing that the wife/kids/estate of the poor schlub who lied on the medical form would see it differently. There's at least one case currently where the decedent never would have been in the water if not for a lie on their medical form. Nevertheless, their estate is suing everyone but the parking lot attendant.
---------- Post added August 15th, 2015 at 11:42 PM ----------
I suspect RJP was talking about "liability" in a sense of risk to people who might need to rescue a diver in trouble, rather than legal liability.
Actually I was speaking from both perspectives, as a crew member on a boat as well as a teaching professional. As someone who has been in a position to jump off a boat to save someone's life as well as someone who will accept you as a student based on the information you've provided me on your medical and other forms... you can bet I'll be pretty upset if one or both of us gets hurt in a situation caused or exacerbated by a medical condition you lied about on your form. You can also bet that some lawyer will convince your widow/widower to sue me if you die while taking a class with me... even if you did lie on the medical form. I'm gonna be pretty ticked about that too.