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Otis Boone insisted he was innocent from the time he was accused of two robberies in 2011, when he was 19. But the two victims who had their cellphones snatched by a knife-wielding man picked Mr. Boone out of separate police lineups. Though there was no physical evidence, he was convicted and sentenced to 25 years in prison.

Mr. Boone, of Brooklyn, took his appeal to New York’s highest court, where a majority of judges ruled that the jury should have been told that witnesses often struggle to identify strangers of a different race because mistaken identifications are a major factor in wrongful convictions. Mr. Boone is black; the victims were white.

The Court of Appeals granted Mr. Boone a retrial and made it mandatory going forward for judges to explain what psychologists call the “cross-race effect” to jurors whenever a case involves a witness identifying of a suspect of a different race.

At his second trial last month, public defenders presented evidence that Mr. Boone was a mile away from one of the robberies five minutes before it occurred. He was acquitted on March 1, after spending seven of the last eight years behind bars.