"The lawyers said their defendants are pleading not guilty," a source at the trial said. "The defense team intends to seek acquittal by all legal means."
Three people have been tried in connection with the attempt to murder Chubais in March 2005, when his car came under automatic gunfire near Moscow: former paratroopers Alexander Naydenov and Robert Yashin, and a former General Staff officer, Colonel Vladimir Kvachkov.
However, the head of Unified Energy System, who also led the country's mass privatizations in the 1990s, was not injured in the attack.
All three defendants have been charged with the attempted premeditated murder of two or more people, and the illegal purchase and possession of weapons, ammunition, explosives and explosive devices.
The criminal case is now being considered by a jury behind closed doors. The judge warned the parties to the trial Tuesday against commenting on the case.
"The judge said he would personally monitor all remarks and commentaries by parties involved in the case, and could impose sanctions, including removal from the trial," said a lawyer acting for one of the defendants.
"We respect the judge's decision and will obey it," said Andrei Shugayev, Chubais' lawyer. But the defendants' lawyers said the trial had been closed to the public for a purpose.
According to prosecutors, the defendants allegedly committed the crime because of their extremist views, and a violent dislike for Chubais, an architect of economic reform in the 1990s which impoverished millions and gave vast fortunes to a handful of well-connected oligarchs, and now a regular author of unpopular decisions to raise electricity tariffs.
The suspects said that not all avenues of inquiry have been studied.
"Not all versions behind the crime have been studied, including a simulation of the assassination attempt," Colonel Kvachkov, the main suspect in the case, said in court earlier.
The court will resume hearings Wednesday, when Chubais could be summoned for questioning.
