Almost 300 lawyers have signed an open letter demanding that Russian authorities stop prosecuting two of their colleagues for allegedly insulting an FSB investigator, the Bumaga news website reported Sunday.

St. Petersburg lawyers Andrei and Mikhail Zlomnov are accused of insulting Dmitry Sablin while they were defending their relative Pavel Zlomnov against charges of arms smuggling last year. The two lawyers face up to a year behind bars if found guilty of insulting Sablin.

The letter accuses investigators of committing several violations, including omitting “any information regarding the Zlomnov lawyers’ insults against Sablin in the procedural documents.”

Pavel Zlomnov, 36, faces up to eight years in jail on arms-smuggling charges and up to five years on charges of justifying terrorism. Law-enforcement officers tortured him during his detention, jumping up and down on him, injuring his kidneys and rupturing his eardrum, Russian media cited him as saying.

A total of 273 lawyers have signed the open letter demanding that St. Petersburg’s chief prosecutor end the Zlomnov lawyers’ prosecution.

Dozens of lawyers from Moscow and St. Petersburg had earlier this year agreed to represent Andrei and Mikhail Zlomnov in court.

The Memorial human rights group has declared Pavel Zlomnov a political prisoner.

“The probable motive for the FSB’s prosecution of Zlomnov is the desire to prevent his release, thereby also intimidating the other victims of torture and taking revenge against him for his allegations,” it said.