Opinion | I Supervised New York City Judges. Juan Merchan Put on a Master Class in the Trump Trial.

I spent almost 13 years as a judge in Brooklyn, Queens and the Bronx. I supervised judges presiding over a wide spectrum of cases, dealing with complex legal issues, angry victims, difficult defendants and intense media scrutiny. The job can at times be thankless and frustrating.

But for all the cases I saw, I never encountered anything remotely as challenging as what Justice Juan Merchan faced in his Manhattan courtroom while presiding over the first criminal trial of a former president. And since Donald Trump was found guilty on 34 counts, Justice Merchan has come under further vicious attack.

As a retiree, I was able to attend each day of the Trump trial. What I saw was a master class in what a judge should be — how one can serve fairly and impartially for the prosecution and the defense, and above all remain a pillar for the rule of law in America.

Since the indictment over the cover-up of hush-money payments was issued last year, Justice Merchan has been subjected to an unrelenting pressure campaign. The defendant, Mr. Trump, and his supporters viciously attacked the judge and his family in deeply personal terms. Most judges strive to maintain their composure under the greatest of stress, but few succeed — yet Justice Merchan remained cool, calm and collected at every step of the trial.

As a supervising judge, I always emphasized the importance of maintaining control to those under my charge. That is how a judge ensures that all defendants — especially the most difficult ones — get a fair trial. That is how everyone is treated with courtesy and how rulings are evenhanded and fair. In this area, Justice Merchan excelled.

He issued a gag order carefully designed to protect witnesses, jurors, prosecutors and court staff, but left himself out of the order. He did this to ensure that the defendant’s right to harshly criticize the proceedings was protected even though he must have known that he would become an even greater target of Mr. Trump’s ire. When Mr. Trump repeatedly violated the order, Justice Merchan bent over backward to avoid sending the defendant to jail, despite a clear legal justification to do so.

It is hard for me to think of another defendant acting out in the same manner who would have received such lenient treatment. But special times — and special trials — sometimes call for special measures. A judge needs to know when to apply such measures.

In the course of the trial, he maintained his composure. Defense attorneys received many favorable rulings, and in some instances (like during the testimony of Stormy Daniels) he even made and sustained objections on behalf of the defense during direct examination. On other occasions, when Mr. Trump engaged in particularly objectionable behavior (like muttering curses about a testifying witness), he calmly called one of the defense attorneys to the bench to put a stop to the inappropriate behavior. Other judges might have called out the behavior directly, embarrassing Mr. Trump in front of the jury, which could be seen as prejudicial to the defendant.

I can’t think of one time when the judge interjected himself unnecessarily against either prosecution or defense, but not everyone agrees with that. In a recent New York Post opinion piece, for example, the lawyer Alan Dershowitz referred to “one of the most remarkable wrongheaded biases I have ever seen” regarding Justice Merchan’s handling of the defense witness Robert Costello’s behavior.

Maintaining order and fairness in a courtroom is not bias; it is how justice is served, and it is no easy thing to obtain.

Since the verdict, Republicans have unleashed further attacks against Justice Merchan. One Arizona Republican running for a House seat called Justice Merchan “a corrupt and biased political operative” and said that he “must be disbarred and prosecuted.”

Let’s be clear, these attacks are not really about Justice Merchan. They are direct attacks on our entire system of justice. As President Biden said in remarks concerning this case on Friday afternoon, they are reckless, dangerous and irresponsible.

However, I do agree with Mr. Dershowitz’s position in that same opinion essay that we should televise trials in New York State, so all could see for themselves what I saw every day and what he saw on the day he was there. For most Americans who followed the case, all they were able to see has come from media gaggles outside the courtroom.

Justice Merchan had to set a boundary between Mr. Trump’s raucous but protected speech (barring transgressions of the gag order) and the fact-based evidentiary and back-and-forth questioning that is central to a trial. By guarding that boundary, he protected the integrity of the rule of law.

I am aware of the deep divisions in our country as to the wisdom and strength of this case. But I am certain that Americans were well served by Justice Merchan.

George Grasso is a retired New York City administrative judge and a former Police Department first deputy commissioner.

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