An individual may be culpable for the crime of attempt if they have the appropriate mens rea, even if they fail to complete the required actus reas of the crime. The central question in attempt liability is how much actus reus is required to trigger attempt liability. The test will vary from jurisdiction to jurisdiction:
- Substantial Step Test - This test, promoted by the Model Penal Code, would require the fact finder to determine if the defendant had taken a "substantial step in a course of conduct planned to culminate in [the defendant']s commission of the crime."
- Res Ipsa Loquitur Test - This test asks whether the individual's attempt is manifesty obvious from the facts.
- Dangerous Proximity Test' - This test asks whether the defendant's actions were in "dangerous proximity to success," or when an act "is so near to the result that the danger of success is very great."
There are several defenses to attempt liability:
- Imposibility - Defendants have often asserted the defense of impossibility to attempt. Several variations of this defense have been argued:
- Factual Impossibility - Although factual impossibility was once recognized as a defense to an attempt crime, it rarely recognized as a defense any longer. As an example, the issue of factual impossibility arises when a police officer uses counterfeit marijunana during a drug operation. Even if the defendant had purchased the drugs, no crime would have existed because the marijuana was counterfeit.
- Inherently Factual Impossibility. Recognized in only one state (Minnesota), the defense applies if the step taken to accomplish the crime was one that a reasonable person would view as inadequate to accomplish the criminal objective.
- Pure Legal Impossibility - If a defendant attempts to achieve a crime, yet the crime does not exist, then legal impossibility is a defense to any prosecution. For instance, imagine an individual who attempts to shoot a deer, falsely believing that the hunting of deer is illegal. This individual would be attempting a crime yet even if the act was completed, no crime would have occured.
- Crimes to which doctrine does not apply - A defendant cannot be found guilty of attempted conspiracy.
- Criminal Negligence - When the required mental state is criminal negligence, it is impossible for the defendant to "attempt" the crime. For example, a person cannot attempt involuntary manslaughter, because intent to act negligently is a logical contradiction.
- Abandonment - Some courts have recognized a limited defense of abandonment. For instance, the Model Penal Code concludes that attempt does not exist if the defendant (1) abandon(s) the effort to commit the crime or prevent the crime from being committed, and (2) their behavior manifests a complete and voluntary renunciation of the criminal purpose. . Abandonment is not a defense if the defendant's motive for abandonment is to decrease apprehension or postpone the commission of the crime to a better time or place.