there was a vehicle and person trespassing on private property. If I'm the landowner (presumably unfamiliar with aviation and gliders) I'd appreciate the policeman figuring out in my absence exactly what was going on in my field. Property rights are among the most fundamental rights we have, of more value to me than the alleged right to remain silent.
Well, this is one way to look at it. Certainly, there was a vehicle and a person on another's private property, no question of that. However, was it a trespass? Now we're splitting legal hairs at this point. A plane landing on another's private property could be an unforeseen circumstance. Much like an auto accident where one of the cars winds up off the side of the road on private property. That is not the case of a trespass, it's just the result of an accident, and absent malicious intent no criminal charge with respect to the car/person on the private property.
Having said that, this was a sailplane, so maybe the circumstance was not so unforeseen. A plane has to come down somewhere, and there is a certain probability that says it will come down on private property(I would say a pretty high probability) if landing out.
Having said that -- it's my op-ed that this was not unforeseen, such as an accident, but neither was it a malicious intent to trespass. It's one of those gray areas and the property owner certainly is justified in maintaining his property rights, but the plane pilot in the interest of safety picked the least objectionable place to land, although it was privately owned.
Now, we are at the point of contention. Did the pilot perform his required duty to present his pilots license to the LEO? Or did he refuse to identify himself? If the former, he's complied with the minimum needed to meet the regs/law, and after that is not required to do anything else. It's been my understanding, and I'm pretty secure that not assisting an LEO in his investigation when one is the subject of that investigation is not grounds for an arrest. i.e., you can't be arrested for not assisting in your own criminal investigation, such is the broad nature of the 5th amendment.
To make this more clear in statement, once you've done what's required by regulation beyond that you can stand mute, or given recent SCOTUS decision you can affirmatively decline to answer questions. If I read the recent decision right, standing mute is still not grounds for arrest, but failing to invoke your right to self-incrimination can be used as a basis for a finding of criminal activity. Which I completely disagree with, but hey - I'll play along and affirmatively decline to assist or answer questions. At that point, the LEO has no basis for arrest, and the arrest was a violation of the civil rights of the pilot.
If on the other hand, the pilot did not identify himself as required to LEO, and did not affirmatively decline to remain silent, then he's kinda screwed. So - I will provide my id as requested, and after that affirmatively decline, and let things go as they will. Eventually, this too will get to the SCOTUS and they will further split the hair of how a citizen should act in the presence of LEO.