Prosecutors arrested Alexei Frenkel in January last year in connection with the murder of former first deputy Central Bank chairman Andrei Kozlov. Frenkel is being held in Moscow's Matrosskaya Tishina detention center.
Kozlov, who oversaw bank licensing and had led efforts to close down dozens of banks for violations of banking legislation, in particular on money laundering, was shot dead along with his driver on September 13, 2006. Kozlov had closed down Frenkel's VIP Bank three months prior to the murder.
"Today at 2 p.m. Moscow time [11 a.m. GMT] my defendant was put in solitary confinement for a period of 15 days without any explanations given," Viktor Parshutkin said. "I believe this was done to deliberately wear him down before the court trial."
A spokesman for the Russian Federal Penitentiary Service said that Frenkel was put in solitary confinement for systematic violations of regulations.
The Prosecutor General's office said earlier today that the probe into the 2006 murder of Andrei Kozlov had been concluded, and the case had been sent to court for trial.
"Deputy Prosecutor General Viktor Grin endorsed the criminal case against banker Alexei Frenkel and his accomplices. They are charged with the murder of Andrei Kozlov, former first deputy chairman of the Central Bank," prosecutors said in a statement.
Frenkel has been faced disciplinary measures at the detention center on several occasions. In November last year he was placed in the isolation ward for 10 days for passing notes between cells. A month earlier, he got 15 days in the ward for drinking alcohol.
Following his arrest Frenkel, who could face life in prison, published two letters accusing the Central Bank of accepting bribes in exchange for allowing banks to join the deposit insurance system. Prosecutors are investigating Frenkel's accusations.
In all, seven suspects are now in custody for their alleged involvement in Kozlov's murder, including Liana Askerova, a restaurant owner, whose testimony eventually led to Frenkel's arrest.