Legal impossibility is a criminal defense that says you can’t be convicted of attempting a crime that doesn’t exist. If the act you set out to do, carried out exactly as you planned, wouldn’t actually break any law, there’s no crime for you to have “attempted.” The defense has a long common law history, but most modern courts have narrowed it so sharply that defendants who genuinely believed they were committing crimes can still be convicted of attempt, even when completing the act would have been perfectly lawful.
What the Defense Actually Says
The idea is simple on its face. Criminal intent, no matter how clear, does not turn a legal act into a criminal one. If you run a poker game in a Las Vegas apartment fully believing you’re breaking gambling laws, you haven’t committed a crime, because gambling there is legal. There’s nothing for the law to punish and nothing for an attempt charge to attach to.
The Fifth Circuit phrased it this way in United States v. Oviedo: “Legal impossibility occurs when the actions which the defendant performs or sets in motion, even if fully carried out as he desires, would not constitute a crime.”1OpenCasebook. United States v. Oviedo The obstacle isn’t a stroke of bad luck in the physical world. It’s the statute book: nothing in it prohibits what the person was doing.
Legal Impossibility Compared to Factual Impossibility
This distinction matters more than almost anything else in this area, because factual impossibility is almost never a valid defense, while legal impossibility sometimes still is.
Factual impossibility is when a person fully intends to commit a real crime, but a real-world circumstance they don’t know about prevents them from pulling it off. The classic example is a pickpocket who reaches into an empty pocket. Picking pockets is a crime, the thief meant to steal, and the only reason nothing was taken is that there was nothing there. Courts almost universally reject factual impossibility as a defense, because the intent was criminal and the act would have been criminal if the world had cooperated.2Legal Information Institute. Impossibility
Legal impossibility is the mirror image. The defendant’s intent may be to do something criminal, but the act itself, if completed, wouldn’t violate any statute. The problem isn’t an empty pocket. The problem is that no law covers the finished conduct.
In practice, courts have found the line between the two maddeningly hard to draw. The same facts can often be framed either way depending on whether you focus on the defendant’s physical acts or on their criminal objective. Someone who sells talcum powder believing it’s heroin is performing a non-criminal act (selling powder) in pursuit of a criminal objective (distributing narcotics). Different courts on nearly identical facts have landed on opposite sides.3OpenCasebook. Criminal Law Casebook – Notes and Questions-Impossibility
Pure vs. Hybrid Legal Impossibility
Because the legal-versus-factual line kept collapsing, scholars split legal impossibility further into two kinds: pure and hybrid. The difference tells you whether the defense will actually work.
Pure Legal Impossibility
Pure legal impossibility exists when the defendant believes conduct is criminal, but no law prohibits it. The Las Vegas poker example is the cleanest version. Another: a person who takes home office supplies believing petty workplace theft is a felony, when in fact no criminal statute covers the specific conduct. The guilty conscience is real, but there is no crime to attempt. Pure legal impossibility remains a valid defense in essentially every jurisdiction, including those that follow the Model Penal Code.
Hybrid Legal Impossibility
Hybrid legal impossibility is where real cases live, and where the defense almost always loses. In a hybrid case, the defendant’s goal is genuinely illegal, but a factual circumstance they don’t know about means the legal elements of the crime can’t be satisfied. Common examples:
- Buying property you believe to be stolen, when the goods had actually been recovered by police and returned to the owner before the sale.
- Offering money to someone you think is a juror, when the person is really an undercover officer with no role in the case.
- Sending sexual messages to someone you believe is a minor, when the person on the other end is an adult law enforcement agent.
In each case, the defendant wanted to do something illegal and took steps toward it, but a missing factual element means the completed act wouldn’t technically meet every element of the offense. The New York Court of Appeals handled exactly this scenario in People v. Jaffe, where a defendant tried to buy cloth he believed was stolen. The court held that because the goods had already been returned to their owners before the sale, there was no stolen property to “receive,” and the conviction couldn’t stand.4New York State Unified Court System. People v Jaffe
That reasoning fit older common law principles. Today, Jaffe is widely treated as exactly the kind of result modern criminal law was rewritten to prevent.
How the Model Penal Code Gutted the Defense
The Model Penal Code, which has shaped criminal law in most states since the 1960s, was deliberately designed to eliminate the impossibility defense in nearly every situation. The drafters were frustrated that the legal-versus-factual split produced inconsistent and often absurd results, and they abandoned the distinction.5Oklahoma Court of Criminal Appeals. Impossibility Unavailable as a Defense
The pivotal language appears in Section 5.01(1)(a), which defines attempt as occurring when a person “purposely engages in conduct which would constitute the crime if the attendant circumstances were as he believes them to be.”6OpenCasebook. Ball/Oberman Crim Law Casebook – MPC on Attempt Liability That phrase does the work. A court asks: if the world were the way the defendant believed it to be, would the completed act be a crime? If yes, the defendant is guilty of attempt no matter what the circumstances actually were.
Apply that to Jaffe. If the cloth had actually been stolen, as Jaffe believed, buying it would have been receiving stolen property. Under the MPC, that’s enough. The fact that the cloth had been returned to its owner doesn’t matter. A technical missing element doesn’t matter. Jaffe believed the circumstances made his conduct criminal, and he acted on that belief. The commentary to the MPC’s drafts stated that the Code’s purpose was “to reverse the results in cases where attempt convictions have been set aside on the ground that it was legally impossible for the actor to have committed the crime contemplated.”5Oklahoma Court of Criminal Appeals. Impossibility Unavailable as a Defense
Pure legal impossibility is the only form that survives under this approach, which makes sense: if no law actually prohibits the conduct, there’s nothing to attempt regardless of what the defendant believes. But hybrid cases, sting operations, and scenarios where the defendant’s criminal purpose is obvious all fall within reach of the MPC’s rule.
Sting Operations and Why Defendants Keep Losing
The practical effect of the MPC shift shows up clearest in law enforcement stings. When an undercover officer poses as a drug dealer, a corrupt official, or a minor in an online chat, defendants routinely argue that completing the intended act was impossible because the “drugs” were fake, the “official” had no authority to be bribed, or the “minor” was an adult. Under traditional impossibility analysis, some of these arguments had traction. Under the MPC, they go nowhere.
In Oviedo, the defendant sold what he believed to be heroin to undercover agents. The substance turned out to be procaine hydrochloride, a legal compound. The Fifth Circuit wrestled with whether this was legal impossibility (selling procaine isn’t a crime) or factual impossibility (distributing heroin clearly is). The court acknowledged that the traditional categories weren’t especially helpful.1OpenCasebook. United States v. Oviedo
That kind of analytical mess is exactly what the MPC was designed to short-circuit. Under its “circumstances as he believes them to be” test, the answer in Oviedo is straightforward: the defendant believed he was selling heroin, selling heroin is a crime, and attempt liability attaches regardless of what the substance actually was. Courts in MPC-influenced jurisdictions apply the same reasoning to online sting cases, fake drug sales, and similar setups.
Where Impossibility Fits in an Attempt Charge
Attempt generally requires the prosecution to prove two things: that the defendant intended to commit a specific crime, and that they took real steps toward committing it. Under the common law, those steps had to bring the defendant dangerously close to completion. Under the MPC, a “substantial step” that strongly corroborates criminal intent is enough, which catches defendants earlier in the process.7Legal Information Institute. Attempt6OpenCasebook. Ball/Oberman Crim Law Casebook – MPC on Attempt Liability
Legal impossibility attacks the first element. In a pure legal impossibility case, the defendant intended to do something they wrongly believed was illegal, but no crime covers the conduct, so there’s nothing to attempt. In a hybrid case under modern law, courts look past the missing factual element and ask whether the defendant’s intended conduct, under the facts as they believed them, would have been criminal. If so, the attempt charge stands.
Why the Defense Rarely Works Today
Legal impossibility is far less useful than most people assume when they first hear about it. Pure legal impossibility is valid everywhere, but it’s genuinely rare. Most situations that feel like legal impossibility turn out to be hybrid, and most modern courts reject the hybrid version. The MPC’s “circumstances as he believes them to be” standard has become the dominant approach, and under it, a person who believes they’re committing a crime and acts on that belief can be convicted of attempt even when completing the act was impossible.
The common law approach that produced Jaffe, where a defendant walked free because stolen goods turned out not to be stolen, has been deliberately overruled in most jurisdictions.4New York State Unified Court System. People v Jaffe Legislatures and courts made a policy choice: someone who shows clear criminal intent and takes real steps toward a criminal goal shouldn’t escape liability because of circumstances they didn’t know about. The defense survives in its purest form, but the situations where it actually applies are narrow enough that defense attorneys usually look for other grounds first.