From what I gather, judges usually rule key disclosure when the government already knows the information in the device and it's not for getting new evidence but making the evidence available to the court. In any case I don't think the cops can just lawfully request your key, like they can't search your house without a warrant on normal occasions. My question is what happens if you forgot your password for real? Is there any possibility for them to deny that you forgot it except rubber-hose cryptanalysis?

Source: https://en.wikipedia.org/wiki/Key_disclosure_law#United_States