Nurse, a 30-year veteran of martial arts and a well-respected Muay Thai trainer based out of New York, was tasked with two things: apply Vaseline to the brow, cheekbones, bridge of the nose and temples of the champion's chiseled face, and utilize a pressure-point holistic technique that apparently delivers an energy boost.
What the world saw was Nurse, the back of his left hand acting as a palate for a finger of Vaseline, massage grease into the champion's face, shoulders and back. NSAC inspectors, reacting to people at ringside who took the application as an attempt to give St. Pierre an unfair advantage, scolded Nurse between the first and second, and the second and third rounds.
"I was in the Octagon and they came in screaming: 'On his face! On his face!' I really didn't know what they were saying," Nurse said of NSAC inspectors. "I see it now. In the heat of the moment, I've got a minute to get in there, keep him calm, do my energy work on him, elevate his legs and then he listens to Greg. What they were screaming at me about, I didn't know. Had they said 'You're putting Vaseline on his back' it would have put two and two together."
The idea that Nurse should know better is absolutely true. His experience in fight sport plus common understanding of the Unified Rules of MMA should be more than enough to prevent something like this from happening. But even acknowledging that, whether or not Nurse should've known better doesn't answer the question of whether he actually did in this case. Ignorance of the rules or an innocuous act of not adhering to them doesn't absolve guilt, nor does it address whether whatever was applied to St. Pierre (and the amount is not really known) truly made a difference in the fight outcome.
I also find Nurse's argument that attempting to cheat out in the open seems awfully foolish. So while I find Nurse to be culpable, the truth that fans of either fighter must accept is that determing what Nurse's actions actually did to the outcome of the fight are virtually impossible to quantify. Punitive action by the athletic commission is necessary, but determing guilt based on the amount of problems Nurse's actions may have caused is going to prove exceptionally difficult.