The factual or legal impossibility of committing the offence is not a defence if the offence could have been committed if the circumstances had been such as the perpetrator believed them, nor is it a defence that the attempted offence was actually committed by the accused. Factual impossibility is not a defense under Colorado law against attempted crime. The abolition of the de facto impossibility exception is codified in Colorado`s Criminal Attempt Act – reproduced above. Factual impossibility is the opposite of a “factual error” defence. A factual error occurs when a person is not aware of the circumstances that actually exist. Whereas factual impossibility exists when the person believes that a circumstance exists, when in reality it does not exist. Legal impossibility exists essentially when the accused wants to commit an act that he considers criminal. However, his actions are not illegal. In this case, the respondent`s misunderstanding concerns the law itself.
In other words, he mistakenly believes that the law criminalizes his actions, when in reality it does not. In such a case, the defendant will be able to initiate an impossible defense. For example, the Model Penal Code (MPC), which serves as a model for the penal codes of many states, prohibits de facto impossibility as a defence in attempting to commit a crime by defining attempted conduct as “intentional conduct that would constitute the crime if the circumstances surrounding them were such as it believes they are”. Crimes are committed when all the elements, the parts that make up the crime itself, are completed. Legal impossibility is a complete defence to a criminal investigation, unless there is a law at the time of the acts in question that prohibits those acts and makes them a crime. A person who asserts a legal defense of impossibility can effectively perform all the intended actions. They may have taken all the necessary steps to accomplish what they believe to be a crime, but the performance of these intended acts does not correspond to the established elements of the crimes listed in the Colorado Penal Code. There are two types of defences of impossibility : factual impossibility and legal impossibility. It is factually impossible if the accused wishes to commit an act which, if successful, would constitute a criminal offence but would prevent him from actually committing the offence because of certain factors of which he does not know. In the present case, the defendant`s error lies not in the factual law, but in the factual circumstances of its actions.
This is considered a factual impossibility, and the factual impossibility is not a defense against an attempt. See People v. Fiegelman, 33 Cal. App. 2d 100 (1939). For example: An incapacity defense is a criminal defense that is sometimes used when a defendant is charged with a failed criminal attempt solely because the crime was factually or legally impossible.  Factual impossibility is rarely an adequate defence at common law. This should not be confused with a “factual error” defense, which can be a defense against a specific intentional crime, such as theft.  There are two types of impossibility defenses: legal impossibility, which can serve as a defense against attempt, and factual impossibility, which is generally not possible. Legal impossibility means that the defendant believes that what they are trying to do is illegal, even if they are not. The impossibility of the facts means that the accused could not carry out the attempted crime because the facts are not as he believes them.
The Model Penal Code prohibits factual impossibility as a defence by stating that conduct is an attempt if the accused “intentionally engages in conduct that would constitute the crime if the circumstances were such as he believes them” (Model Penal Code, § 5.01 (1) (a)). In addition to the lack of evidence against the criminal act and criminal elements of intent, legal impossibility and voluntary waiver can also serve as a positive defense in many jurisdictions. There are several possible defences that can be used when an accused is charged with an attempted crime. The first is impossibility. In a situation where the accused believes that he or she may commit a crime, but that it is impossible for reasons unknown to him or her to actually commit the crime, acts that would normally be sufficient for a conviction cannot, in certain circumstances, constitute an attempt because the crime cannot actually be committed. The legal impossibility defense means that the defendant believes that the crime they were trying to commit was illegal – but in fact – it is not illegal. Even for the crime of attempt, a defendant who engages in conduct that he considers illegal but is not illegal cannot be convicted of an attempt. Look at the example from section 8 “Test Res Ipsa Loquitur” with Melissa and Matthew and the attempted poisoning of the neighbor`s dog. Suppose Melissa is eighteen. Melissa believes that a person must be twenty-one years old to buy rat poison because it is the law in the state where she lived five years ago. In fact, the state where Melissa currently lives allows the purchase of rat poisons by eighteen years or older. The first store Melissa enters asks for ID when she tries to pay for rat poison, so Melissa apologizes and leaves.
The second store, which Melissa enters, does not ask for identification and she successfully buys rat poison. Melissa probably wasn`t trying to illegally buy rat poison from the first store she entered. Melissa`s act of buying rat poison is legal under the circumstances. Therefore, her erroneous belief that she is attempting to commit a crime does not transform that legal act into an illegal act. It is impossibility if the facts at the time of the attempt make the crime contemplated impossible, although the accused was not aware of it at the time of the attempt.  In People v. Lee Kong, 95 Cal. 666, 30 P. 800 (1892), the accused was convicted of attempted murder for shooting a hole in the roof, believing his victim was there, and even where his victim had been moments before, but not at the time of the shooting.  Another case involving the defence of factual impossibility is Commonwealth v. Johnson, in which a psychic healer was charged and convicted of fraud, even though a fictitious name was used to catch him.
In United States v. Thomas, The court found that men who believed they were raping a drunken and unconscious woman were guilty of attempted rape, even though the woman had actually died at the time of sex. On the other hand, with very few exceptions, factual impossibility is difficult to assert and is also excluded by law as a defense to the principal crime against which it can be invoked, the crime of attempt under Colorado law. See the example with Melissa and Matthew in section 8 “Test of Res Ipsa Loquitur”.