[DonaldFisk]

What if the trespassers just ignore the sign, and walk on/over the privately owned land without the landowner ever becoming aware of it? How could the landowner sue the unknown trespassers when there wasn't even any evidence of their trespassing?

[ttymck]

What about a security camera?

[DonaldFisk]

What about a security camera? What can the landowner do if they've already left the private land without committing any crimes?

[ttymck]

Yes, that's what I was asking. Your previous comment indicated the homeowner needed evidence in order to sue for trespassing. But it seems there was no crime committed after all.