Unit 35: Necessity


  • Dressler 271-282

  • Nelson (CP)

  • Schoon (CP)

  • Dudley & Stephens (CP)

Key Terms: 

  • necessity

  • civil disobedience


A necessity (or “choice of evils”) defense arises when an individual must choose between committing a lesser harm or allowing a greater harm to occur.  A classic example of necessity is preemptively burning down a house in order to prevent a wildfire from spreading.

Necessity is a “defense of last resort;” it justifies otherwise illegal conduct based on principles of justice, utility, or common sense.

Some jurisdictions limit necessity to circumstances arising from a “non-human condition” (like a natural disaster), while disallowing it in man-made cases (such as a runaway truck). Some jurisdictions have also limited the availability of necessity to cases involving the protection of persons or property.

Although most jurisdictions do not precisely define necessity, it is generally recognized if the following six conditions are met:

1)   There must be a clear and imminent danger.

2)   The actor must believe that his conduct will effectively diminish the danger, and this belief must be reasonable.

3)   There must not be an effective legal recourse.

4)   The harm the defendant reasonably foresees causing must be of a lesser degree than the harm the defendant seeks to avoid. The defendant’s analysis and choice need not be objectively correct, as long as they are rational and correct based on what the defendant knew and could reasonably foresee. For example, with the wildfire hypothetical above, suppose the house that the defendant burned down was actually occupied by several people. If the defendant had no reasonable way of knowing that the house was occupied, then the fact that those individuals died would not be considered in the analysis.

5)   The legislature must not have already weighed the competing values and decided contrary to the defendant.

6)   The defendant must not have substantially contributed to the initial threat, or come to the harm. In other words, a necessity defense is not available to someone who knowingly puts himself in danger without cause, and then must break the law in order to avoid the danger.

Civil Disobedience

Civil disobedience is the public, non-violent performance of illegal conduct for the purpose of challenging law or government policies. Individuals who engage in civil disobedience typically refrain from physical violence against individuals or property, and some sources define civil disobedience in part by its non-violent nature. However, some argue that civil disobedience can be violent, so long as the violence is purposeful.

Civil disobedience can be direct (where the broken law and the challenged law are the same), and indirect (where the broken law and the challenged law are different). A necessity defense is unavailable in virtually all indirect civil disobedience cases. It is also unlikely to succeed in direct civil disobedience cases because some or all of the six conditions are not likely to be met. Some commentators have argued for a “political necessity” defense to be available in civil disobedience cases. 


May a necessity defense be used in homicide case, when the killing of one (or several) innocent people results in sparing a greater number in individuals? At common law the answer is no, and some American courts have explicitly stated this. Consider Dudley and Stephens. Can the ruling in that case be applied to all necessity defenses in homicide cases? 

Model Penal Code

The Model Penal Code recognizes a necessity defense if three requirements are met: first, the actor must believe his conduct to be necessary to avoid harm to himself or another. Second, the harm caused must be less than the harm the actor seeks to avoid. Finally, the legislature must not have plainly expressed an intent to exclude the actor’s conduct in the particular situation. This does away with the common law’s imminence requirement, and allows the defense in cases where the actor is responsible for the harm done. However, if the actor behaved recklessly or negligently in bringing about the initial harm, and is charged with recklessness or negligence, then the defense becomes unavailable. Finally, the MPC does not limit the necessity defense’s applicability; it can be used in cases involving non-natural disasters, as well as in homicide cases.

Questions for Review:

Q1. The above summary was written with the assumption that necessity is a justification, not an excuse. Do you agree with this assumption? Why or why not?

Q2. Do you think a necessity defense should be available in homicide cases? Explain your reasoning.

Q3. Assume for the sake of argument that the necessity defense had been successful in Dudley and Stephens. Should the defense in that case have been viewed as a justification or an excuse? Consider utilitarian and retributivist reasoning in your answer.

Q4. Should a necessity defense be available in cases of direct civil disobedience? What arguments support or challenge your view?

Q5. Karen is driving her car up a hill, when she notices up ahead that a truck driver has lost control of his vehicle and is careening down the hill at a breakneck speed. Although the truck is still a little ways off – about 40 seconds – the road is narrow and there isn’t anywhere safe except for a shoulder pullout. However, there’s only room for one car in the shoulder, and there is a parked car already there. The only way for Karen to move her car into the shoulder would be to push the parked car over the hill and down a slope. Karen decides fast, and drives into the shoulder, pushing the car over. Karen makes it out okay, but unfortunately Joel was taking a nap in the parked car, and suffered serious injuries from the car’s fall. Can Karen successfully argue a necessity defense for pushing Joel’s car over the hill? Assume that the jurisdiction allows a necessity defense in cases not involving natural disasters.