KYIV -- Former Ukrainian President Viktor Yanukovych is being tried in absentia on high treason charges in Kyiv.
The trial began on May 4 at the Obolon District Court in the capital, with two lawyers representing Yanukovych.
Yanukovych abandoned office in late February 2014 and fled to Russia in the face of massive protests triggered by his decision to scrap plans for a landmark deal with the European Union and improve trade ties with Moscow.
Dozens of people were killed in attempts to clamp down on the protests.
Yanukovych, who remains in Russia, is accused of treason, violating Ukraine's sovereignty and territorial integrity, and abetting Russian aggression.
In the wake of Yanukovych's downfall, Russia seized control of the Crimean Peninsula and fomented separatism across eastern and southern Ukraine.
Kyiv and NATO say Moscow has given separatists who took over parts of the eastern Donbas region substantial military support in a war that has killed more than 9,900 people since April 2014.
Ukrainian authorities say a key piece of evidence against Yanukovych is a letter in which they say he asked the Russian leadership to intervene.
Russia's ambassador to the United Nations at the time, the late Vitaly Churkin, displayed the letter at a UN Security Council meeting on March 4, 2014, two weeks before Moscow claimed to have completed the procedure of making Crimea part of Russia.
A man officials say was a key witness in the case, former Russian lawmaker Denis Voronenkov, was shot dead in broad daylight in Kyiv on March 23.
Ukrainian authorities called the slaying of Voronenkov, who had defected to Ukraine in October, the "public killing of a witness" in the case.
Ilya Ponomaryov, another former Russian lawmaker who has left Russia, is expected to testify as a witness. Ponomaryov was the only member of the State Duma, Russia's lower parliament house, to vote against the annexation of Crimea in 2014.
After a debate between the state prosecutor and defense lawyers at the court session on May 4, Judge Vladyslav Devyatko ruled that Yanukovych should be given the opportunity to take part in the trial by video-link.
The judge then adjourned the proceedings until May 18.
The Ukrainian Prosecutor-General's Office said on May 3 that the international police agency Interpol had ceased searching for Yanukovych, adding that the decision will be appealed.
Yanukovych could be sentenced to 15 years in prison if convicted, but he is protected by Russia and would be unlikely to travel to Ukraine and serve the time.
At least seven other probes have been launched by Ukrainian authorities against Yanukovych, who was elected president in February 2010.
The charges against him range from corruption to involvement in the mass shooting of unarmed protesters in Kyiv in February 2014 as the standoff between his government and the Euromaidan demonstrators came to a head.