After five months, the death penalty trial of Ronell Wilson had entered its last few minutes when a federal prosecutor presented some parting thoughts for the jurors to consider as they deliberated.

If Mr. Wilson, who had executed two undercover police officers on Staten Island, truly accepted responsibility for the killings, why had he not pleaded guilty? And if Mr. Wilson truly felt remorse for his actions, why had he not taken the witness stand to say so?

It is not known whether those statements contributed to the jury’s decision to issue the first death sentence in New York in more than a half century. But what is clear is that this week, three and a half years after the sentence was issued, those statements have spared Mr. Wilson from lethal injection, at least temporarily.

A three-judge panel on the United States Court of Appeals for the Second Circuit decided on Wednesday to vacate the death penalty sentence Mr. Wilson received in Federal District Court in Brooklyn, citing the prosecutor’s statements in the penalty phase that they said violated the defendant’s constitutional right.