Case brief summary
To be guilty of helping someone commit a federal crime (called aiding and abetting), a person must do something that helps the crime happen and must intend for the whole crime, including all its key parts, to succeed.
Facts
A marijuana sale went wrong when the buyers grabbed the drugs and ran, and someone in the sellers car fired a gun at them. It was unclear whether Rosemond or another person in the car was the shooter.
Procedural history
Rosemond was convicted of using a gun during a drug deal based on jury instructions that didn't require him to know about the gun beforehand. An appeals court upheld this, so the Supreme Court took the case.
Issue
What must the government prove to convict someone of helping another person use a gun during a drug crime, when the defendant himself may not have been the one holding the gun?
Holding
The jury instructions were wrong because they didn't require proof that Rosemond knew about the gun early enough, before it was used, while he was helping with the drug deal.
Reasoning
Helping with any part of a crime involving two steps can count as helping with the whole thing, but only if the person knew about both parts in time to still choose to walk away.
Opinions
Majority (Kagan): Active participation in the drug deal plus advance knowledge that a companion would have a gun is required to convict someone of helping commit the gun crime.
Concurrences (Alito): Agreed with most of the majority's reasoning but noted disagreement over how advance knowledge interacts with defenses like duress and necessity.