The 30-year prison sentence handed down to Shahawar Matin Siraj for his plot to blow up the Herald Square subway station is a victory for all New Yorkers in the war against Islamist terrorism. In the pursuit of such victories vigilance is essential at the local level. Over the course of the case there was so much hand wringing about alleged overreaching by the police that the point just needs to be made over and over. But for the undercover work of the New York Police Department, Siraj might well have caused many deaths and wreaked real havoc on our city, all in support of a classic Islamist extremist ideology.

An immigrant from Pakistan, Siraj was arrested shortly before the Republican National Convention as the result of an investigation launched by the NYPD’s Intelligence Division. During the case, testimony was given by a detective, Stephen Andrews, about how, as it was characterized in a May 11 news story by our Joseph Goldstein, he ran surveillance of the al-Noor mosque on Staten Island and the Islamic Society of Bay Ridge. He worked with an informant, Osama Eldawoody, who Detective Andrews said, “was supposed to be on the lookout for whatever was going on. His eyes and ears were to be open.” Mr. Eldawoody attended about 575 services as a police informant over a 13-month period, before monitoring Siraj.

The case against Siraj was also made by an undercover officer of Bangladesh origin known by the pseudonym “Kamil Pasha,” who’d had even earlier contact with Siraj. This meant, our Mr. Goldstein reported, that before police knew of a plot, “the department already possessed detailed reports of Siraj’s political views and his often violent and inflammatory statements, which recorded his satisfaction at the loss of the space shuttle Columbia and his support for Osama bin Laden.” Police tactics elicited bitter objections from Siraj’s attorneys, one of whom, Martin Stolar, is quoted today by Mr. Goldstein as saying that the NYPD “was able to create a crime and then solve it in order to be able to claim a victory in the war on terror.”

But one of the wonderful elements about American courts is that everyone gets a chance to make his argument and then a jury weighs the facts. There are other safeguards. The judge in the case, Nina Gershon, who had served as a magistrate for 20 years before being elevated to a judgeship by President Clinton, could have stopped the proceedings at any point. Commissioner Kelly issued a statement calling the sentence handed down today “a milestone in the safeguarding of New York City. It says that those who conspire against New York will pay a severe price. It also reinforces the outstanding work of the Police Department’s Intelligence Division. Our detectives uncovered a murderous plot in its infancy and stopped it before lives were lost. This sentence is a tribute to them.”