Elements of necessity:
- The defendant must be faced with a clear and imminent danger.
- The defendant must have a reasonable expectation that his action will be effective in abating the danger he seeks to avoid.
- There must be a direct causal relationship between his action and the harm to be averted.
- There must be no effective legal way to avert the harm.
- The harm that the defendant will cause by violating the law must be less serious than the harm he seeks to avoid.
- The defendant’s actions should be weighed against the harm reasonably foreseeable at the time, rather than the harm that actually occurs.
- Lawmakers must not have previously “anticipated the choice of evils” and determined the balance to be struck in a manner which conflicts with the defendant’s choice.
- The defendant must come to the situation with “clean hands”. He must not have substantially contributed to the emergency.
Some states limit the defense to emergencies created by natural, non-human forces.
Some courts only allow necessity to protect people and property.