The final phase of the nine-month trial of Mikhail Khodorkovsky, former boss of Russian oil giant Yukos and once the country's richest man, began on Monday.
Platon Lebedev (right) and Mikhail Khodorkovksy (left) are close allies
Prosecutor Dmitry Shokhin said Mr Khodorkovsky's guilt and that of Yukos shareholder Platon Lebedev was proven.
The two are accused of tax evasion and of acquiring 20% of Apatit, a fertiliser company, illegally in 1994.
The court heard their cases but ran out of time for third defendant Andrei Krainov. The case continues on Tuesday.
Andrei Krainov is a former director of Volna, the company which acquired the Apatit shares.
Supporters of Mr Khodorkovsky and Mr Lebedev maintain that the Russian state is punishing Mr Khodorkovsky and a number of other Yukos executives because of Mr Khodorkovsky's involvement in Russian politics.
However, President Vladimir Putin has repeatedly said that the investigations were designed to make Yukos and its employees comply with the law and pay their back taxes.
Prosecutors have previously requested 10-year sentences for Mr Khodorkovsky and Mr Lebedev.
"The indictment has found in the court complete confirmation, despite the denial by Khodorkovsky and Lebedev and partly by Krainov, of their guilt," Mr Shokhin told Meschansky Court in Moscow on Monday.
The recent conviction of Alexi Pichugin, former Yukos security chief, on the grounds of murder and attempted murder may provide an indication as to how Moscow is likely to treat Mr Khodorkovsky and Mr Lebedev.
Mr Pichugin was convicted on Thursday and is expected to receive his sentence on Wednesday.
Mr Khodorkovsky's lawyers are expected to ask for five working days to prepare a statement. The judge is then likely to adjourn the hearings while a verdict is decided.