The European Court of Human Rights says it cannot rule on whether or not Russia properly investigated a Soviet World War II massacre of Polish officers.
Fifteen Poles have complained that Russia failed to hold a proper investigation into the killing by the Soviet secret police of some 22,000 Polish officers and intellectuals in the Katyn Forest in 1940.
The Strasbourg-based court said it had not received vital documents from Russia to properly judge the case.
It also said Russia failed to notify it that it closed its investigation into the massacre in 2004.
The judges also ruled that Russia's response to attempts by the victims' relatives to find out the truth about what happened at Katyn had amounted to "inhuman treatment."
The ruling is not final and may be appealed within three months.
With reporting by AP and AFP