John is hunting on public land. If John accidentally crosses an unmarked property line of which he is not aware onto Joe's property, is he trespassing?
Your question goes to a person's state of mind, which gets tricky; the intention of the law is that to be guilty of trespassing a reasonable person would need to know they had entered into or were remaining in a place they are not supposed to be. Specific requirements for what that means is going to vary by jurisdiction (closed-off area, posted signs, verbal notice, etc).
Trespass is knowingly entering another owners’ property or land without permission, which encroaches on the owners’ privacy or property interests (Cornell Law).
In your example, John would not be trespassing unless and until Joe asked him to leave and John refused to do so.
This triggered an interesting foray into a rabbit hole. Google provides the common definition of "enter the owner's land or property without permission" - no reference to state of mind. Missouri's definition: revisor.mo.gov/main/… says in part, "A person commits the offense of trespass in the first degree if he or she knowingly enters unlawfully or knowingly remains unlawfully in a building or inhabitable structure or upon real property." Aug 23, 2022 at 16:57
This makes me wonder if the legal def varies state by state. Aug 23, 2022 at 16:57
Also, the OP didn't specifically ask for the legal def, but since this is law.stackexchange.com, I'm inferring that's what is asked. Aug 23, 2022 at 16:58
ORS 105.700 establishes statutory liquidated damages of $1,000 for trespassing (in addition to actual damages), as long as the land is closed and the defendant entered and remained without permission. "Closing" the land is described as:
For land through which the public has no right of way, the landowner or agent must place a notice at each outer gate and normal point of access to the land, including both sides of a body of water that crosses the land wherever the body of water intersects an outer boundary line. The notice must be placed on a post, structure or natural object in the form of a sign or a blaze of paint
(which covers the scenario that you describe, i.e. through public land). In the situation you describe, there is probably no gate near at the boundary between the public and private land, and no normal point of access (such as a driveway).
Since John is hunting, he has likely violated ORS 164.265, a Class A misdemeanor:
A person commits the crime of criminal trespass while in possession of a firearm who, while in possession of a firearm, enters or remains unlawfully in or upon premises.
Note that "premises" is defined in ORS 164.205 to "include any building and any real property, whether privately or publicly owned". If he is hunting without a firearm, it is only a Class C misdemeanor. "Enter or remain unlawfully" is defined
(a) To enter or remain in or upon premises when the premises, at the time of such entry or remaining, are not open to the public and when the entrant is not otherwise licensed or privileged to do so; (b) To fail to leave premises that are open to the public after being lawfully directed to do so by the person in charge; (c) To enter premises that are open to the public after being lawfully directed not to enter the premises; or (d) To enter or remain in a motor vehicle when the entrant is not authorized to do so
Fortunately for John, they also give a definition for "Open to the public", as
premises which by their physical nature, function, custom, usage, notice or lack thereof or other circumstances at the time would cause a reasonable person to believe that no permission to enter or remain is required.
Because the land owner has not adequately notified the public that the land is closed, a reasonable person would believe that no permission is required, therefore the land is "open to the public", but only w.r.t criminal trespassing.