Not ignoring anything. I'm just properly applying the correct standard for the officer to apply in evaluating whether there is PC for arrest and comparing it to the statute.
There are a few "knowing" mens rea...such as knowing, reckless and intentional in which the defendant has knowledge and either intends for the result or knows but ignores a likely risk of the result....and one "un-knowing" mens rea, negligence, where you just have to show that a reasonable person would not have acted like the defendant.
So, the officer is standing on the side of the road with a dude who is in possession of a car, the car has BOTH marijuana AND a secret compartment. The officer almost HAS to assume that the defendant knows of the presence of both, despite what the defendant (who is trying to stay out of jail) is telling him. The fact that the drugs are there, well, the officer would have almost no way of knowing what the defendant REALLY knows...which is why he doesn't have to have BRD proof in order to make the arrest...and even if ultimately there's a ton of RD here.
So, the arrest is OK (and in reality, the damage is done).
The defendant's subjective knowledge (that contained within his skull, which nobody else on planet earth can know) is for the judge/jury to weigh in seeing him answer questions or listening to the other witnesses recount the encounter. Subjective knowledge is for the fact finder, not really the officer...though SOME officers will be really gracious and apply their own crap-detector on scene in deciding whether someone takes a ride...not obligated to, and it's great when they do.
As far as conviction...all of these facts are coming into play, plus add in the jury bias against the defendant, and getting an acquittal starts to look a lot less likely. Yes, the ultimate evidence is the defendant's honest knowledge about the intended use of the compartment...and without a finding that he knew beyond a reasonable doubt that the compartment is used for drugs, he goes home. I am merely stating that his defense of "i didn't know, it wasn't my car, etc." really comes apart when the prosecutor says in opening/closing statements..."AND THERE WAS WEED IN THE CAR!!!" If I were a prosecutor, that case is not getting dropped unless I meet with the defendant and he seems credible and honest and "in the wrong place at the wrong time." This defendant is not exactly the mosty sympathetic, he apparently hangs out with drug users/possessors...a jury isn't gonna ignore that.