Platon Lebedev, who faces theft charges along with jailed Yukos-founder Mikhail Khodorkovsky , will start to give his testimony in court on Monday.
Khodorkovsky and Lebedev are already serving eight-year sentences for fraud and tax evasion. They are now accused of stealing $9.6 billion from the $15.8 billion profit generated by Yukos between 1999 and 2003, as well as 350 million metric tons of oil.
Lebedev will answer questions from the judge, prosecutors and defense for about two weeks.
Konstantin Rivkin, a defense lawyer, said the jailed businessman will give his testimony to "refute information which he considers falsified."
"He wansts to expose everything and reveal in detail what he really did and in which cases investigators and prosecutors provided false information," the lawyer said.
Khodorkovsky has already given his testimony.
In June, Sberbank head German Gref, Russia's former economics and trade minister, and Russian Industry and Trade Minister Viktor Khristenko were summoned as witnesses for the trial at the Khamovniki court.