In the HBO series “The Night Of,” the police think they have solved a murder by arresting a young man from Queens who had a bloody knife in his pocket and was found near the victim’s house after a night of debauchery with her. But a relentless detective named Box cannot resist digging deeper. In the middle of the murder trial, Box tells the prosecutor that he has discovered circumstantial evidence that points to an entirely different suspect.

The prosecutor blows him off.

“We got more on this kid,” she replies, then marches on with the trial, not bothering to share this bit of information with the defense lawyers.

She flagrantly violates the law. The lawyers break so many laws in the courtroom of “The Night Of” that some of them do not even exist yet. But covering up evidence that might help a defendant? There is a real law against that.

Holding back exculpatory evidence is regarded as one of the most serious violations of a prosecutor’s duty — so much so that when it is discovered, there is a great effort by the prosecutors to pretend it did not actually happen.