Twelve alumni of Yeshiva University have joined 19 other former students who are suing the Modern Orthodox flagship university for allegedly covering up decades of sexual abuse at its Manhattan high school for boys.

But the 31 students suffered a setback August 6, when United States District Judge John G. Koeltl denied their attorney’s request to gain access to more information through discovery at a court in Manhattan.

“You’re basically having plaintiffs tied one hand behind their back because much of the information is in the hands of the defendants,” Kevin Mulhearn, the students’ attorney, told the court, according to a transcript.

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In New York, criminal and civil cases of child sexual abuse must be brought before a victim turns 23; the plaintiffs are older, and claim that they were abused during the 1970s and ’80s. Mulhearn, however, argues in the suit that the statute of limitations does not apply, because Y.U. fraudulently covered up the abuse.

Discovery would have given Mulhearn access to internal Y.U. documents and the ability to interview current and former Y.U. employees about the alleged cover-up. It is a legal maneuver he used in a similar abuse case against Brooklyn’s Poly Prep Country Day School, which the school settled with 12 men represented by Mulhearn.

Instead, Koeltl accepted Y.U.’s request for a motion to dismiss the $380 million lawsuit, and gave Y.U. until September 13 to prepare the paperwork.

Referring to an ongoing investigation that Y.U. commissioned from an international law firm, Sullivan & Cromwell, into the abuse allegations, Mulhearn added, “I know that they have conducted a seven-month investigation independently, talked to dozens — if not hundreds — of individuals, with respect to issues pertaining to notice of abuse and the school’s response to notice.

“It would be unfair and prejudicial to the plaintiffs to go forward and have our plaintiffs be put in legal jeopardy on a motion to dismiss without that information being in our possession.”

But Koeltl ruled that Mulhearn would have to survive Y.U.’s motion to dismiss the case before he could begin discovery.

“Complaints are not filed in order to get discovery,” Koeltl said.

Mulhearn argued that discovery should begin promptly because some of the defendants in the case are elderly. He singled out Y.U.’s former president Norman Lamm, who is “rumored to be in ill health.”

Koeltl asked Y.U.’s lawyers to check on Lamm’s health.

Karen Bitar, of Greenberg Traurig, a law firm representing Y.U., said, “Dr. Lamm has a private counsel that has been his attorney for several years now, and I know that he is looking into this issue with Dr. Lamm, and so we will be prepared to discuss that with plaintiffs’ counsel expeditiously.”

Of the case against Y.U., Bitar drew attention to the fact that the alleged assaults took place between 25 and 42 years ago.

“In all candor, it is a very old case,” Bitar said.

On July 17, the New York paper The Jewish Week reported that Sullivan & Cromwell’s investigation into the abuse allegations had cost Y.U. $2.5 million and would be completed in four weeks.

Matt Yaniv, a spokesman for Y.U., told the Forward that he could not comment on the cost of the investigation.

In an August 5 email, Yaniv sent the Forward the following statement: “It is anticipated that the investigation will be finalized and a comprehensive report will be released by Sullivan & Cromwell in the coming weeks.”

Yaniv had given the same statement to The New York Times on July 9.

Contact Paul Berger at berger@forward.com or on Twitter, @pdberger