The case is Langston v. Smith, decided on January 7. Not that Langston is a good guy, or anything. What happened is that the trial court, including the prosecutor, got confused about what it takes to convict someone for felony assault, which criminalizes actions taken "in the course of and in furtherance of the commission ... of a felony" that cause "serious physical injury" to a non-participant.
The statute seems easy enough, but I guess it isn't. Langston helped two confidential informants (they were law enforcement officers) purchase an illegal gun. At the apartment building where the sale was supposed to happen, rather then sell the weapons, the sellers shot one of the officers, Marquez, causing serious injuries. Langston testified that he did not know the shooters. He was convicted of felony assault.
If you are not well-versed in criminal law, you are probably wondering why the habeas petition was granted. The Constitution requires that criminal defendants be convicted beyond a reasonable doubt. In this criminal proceeding, the state courts (including the appellate division, which sustained the conviction) got it all confused. This case was tried as a botched robbery, not as a botched gun sale, but the jury was charged that they could convict Langston if the officers' injuries were in furtherance of criminal possession of a weapon. Langston could not be convicted for this, however, because there was no evidence that he had anything to do with the crime of criminal possession of any weapons. The Second Circuit (Lynch, Feinberg and Newman) writes,
had the jury convicted Langston after being asked to decide whether the assault on Marquez had been committed in furtherance of an attempted robbery, affirmance of that verdict would present no difficulty. However, Langston was not charged with attempted robbery, and the trial judge instructed the jury that to convict Langston of felony assault it had to find, beyond a reasonable doubt, that he or another participant caused ... serious physical injury to Arther Marquez while in the course of and in furtherance of criminal possession of a weapon.
What the prosecution had to do to convict Langston of felony assault was to show that the officers were assaulted "to further the possession of the very guns used in the attack -- the theory on which the State principally defends the conviction in this Court." But, as the prosecutor seemingly admitted, "shooting Marquez was in no way part of a plan to ensure that the guns used in the assault remained in the shooters' possession." Langston had nothing to do with the ambush against the officers. The gunmen appeared without warning and opened fire. While the gunmen certainly did the shooting in furtherance of criminal possession of the weapons, Langston's lack of any involvement in that scheme gets him off the hook for felony assault.