Clashing with the U.S. Attorney's Office in Boston, dozens of defense attorneys for clients charged in the college admissions scandal accused prosecutors Tuesday of using improper judge-shopping tactics to steer their cases.

In a letter sent to U.S. District Chief Judge Patti Saris of the District of Massachusetts, 26 lawyers who represent parents charged in Operation Varsity Blues expressed concern that prosecutors would subvert the random judge-assignment process by adding defendants to a case where the judge was already assigned.

The prosecutors did exactly that shortly after the letter was sent, indicting 16 parents in an already-pending case before U.S. District Judge Nathaniel Gorton.

District of Massachusetts Judge Nathaniel Gorton.

The defense lawyers said they took no particular issue with Gorton, but said there was no basis in federal criminal case rules to link their cases to that of David Sidoo, a parent charged with paying over $200,000 to people who pretended to be his sons and got high scores on the SAT college admissions test. Sidoo's indictment in early March was announced the same day it was revealed that dozens of other parents were charged by complaint.

“We are gravely concerned that the United States Attorney's Office is seeking to evade the district's random assignment process … we think your honor has the ability to deter it from happening,” the defense lawyers wrote. They called on Saris to take “whatever available steps are necessary” to make sure their clients' indictments were randomly assigned.

Andrew Lelling, the U.S. attorney in Boston, personally signed the government's response. He called the defense lawyers' letter “procedurally inappropriate and disingenuous,” saying the government's charging papers make clear that all the parents conspired with William Singer, a corrupt college admissions consultant who cooperated with prosecutors. Adding defendants using a superseding indictment in an already-pending case is “routine,” Lelling wrote.

The prosecutor's letter also accuses the defense lawyers of objecting because they think Gorton imposes longer sentences than other judges in Massachusetts federal court. Removing Gorton would be “unprecedented” and would undermine the very system that the defense lawyers claim they support, Lelling said.

“This morning's letter was inappropriate—a 'Hail Mary' by people who know better and who appear to have leaked the letter to the press right after sending it to you,” Lelling wrote. “I am a veteran federal prosecutor. I take seriously this office's ethical obligations.”

The letter was publicly docketed under its own case number. The defense attorneys who signed the letter include those from Mintz, Levin, Cohn, Ferris, Glovsky and Popeo; Bienert Katzman; Orrick, Herrington & Sutcliffe; Keller/Anderle; Ropes & Gray; Nixon Peabody; White & Case; Nutter McClennan & Fish; Todd & Weld; Miner Orkand Siddall; Boies Schiller Flexner; Duane Morris; and the solo practitioner Martin Weinberg.

The exchange punctuated an already eventful day in the college admissions scandal cases. Prosecutors announced the indictments of 16 people Tuesday, including actress Lori Loughlin, the day after they revealed that 13 parents and one coach had agreed to plead guilty.

Among the parents pleading guilty are Gordon Caplan, the former co-chairman of Willkie Farr & Gallagher who was fired after he apologized for his conduct and announced his plans to come clean. Caplan is set to enter a guilty plea at 2:30 p.m. May 21.