Preliminary hearings in the case of Nadia Savchenko, 34, who has become a symbol of resistance in Ukraine to Russian support for separatists in the east, are scheduled for Thursday in the Rostov region of southern Russia.
Savchenko's lawyer, Ilya Novikov, told a briefing in Kiev he had phone billing data showing that she was already the prisoner of pro-Russian rebels when the journalists were killed.
Savchenko is accused of guiding artillery fire onto identified targets, in this case the location of the journalists.
"According to the billing of Savchenko's two telephones, the first telephone was registered at the centre of Luhansk at 10.44 hrs," Novikov said. The position of the second phone was at a rebel base and registered at 11.04 hrs, he added.
The two Russian journalists were killed in shelling at 11.40 hrs outside Luhansk in June 2014. "If at 10 or 11 hrs she was already in captivity, it completely breaks the Russian version," Novikov said. The defence also held video evidence demonstrating her innocence.
Savchenko, elected a parliamentary deputy in Ukraine after her arrest, is the highest profile Ukrainian prisoner held by Russia. Her plight has turned her into a national heroine at home.
Though a fragile ceasefire seems to be holding, more than 6,500 people have been killed in the conflict in Ukraine's industrialised Russian-speaking east. Moscow denies Western accusations it is backing the rebels with arms and soldiers.
Savchenko, who was held for a time in a Moscow psychiatric clinic, is also charged with crossing the border into Russia illegally and could face 25 years in jail if convicted.
Her relatives say she was spirited out of Ukraine illegally into Russia by the rebels. Ukrainian and Western politicians have appealed to Moscow to free Savchenko. "The sentence has already been approved and it will be as hard as possible," Novikov said.
In Kiev, an advisor to the Ukrainian state security service said two Russian soldiers held by Ukraine earlier this year may go on trial for terrorism in September.
Alexander Alexandrov, one of two Russian officers held, denied to Reuters television there had been any exchange envisaged between him and Ukrainian prisoners held by Russia.
"Those who are fighting should think of their relatives, of their close ones," he said. "And to those who are now on the territory of the Russian Federation (I want to say): you should watch mass media less and try to figure out what's happening yourselves."
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