European Court of Human Rights: photo - echr.coe.int
The case, which has been referred to the court's 17-member Grand Chamber following an April 2011 judgement by a chamber of seven judges, is expected to close with a final judgement by the end of the year.
Among several issues at stake, the Polish applicants are seeking to establish that Russia did not carry out an adequate investigation into the 1940 shootings of over 22,000 Polish prisoners of war.
The 15 Poles are relatives of 12 victims of the killings.
“We are optimistic,” said Ireneusz Kaminski, a member of the Poles' defence team, as cited by the Polish Press Agency (PAP).
“We have prepared a very strong argument making wide-ranging references to international law and the decisions of international courts,” he said.
“We hope that there will be no surprises on the part of the Russians,” he added.
Moscow officially admitted guilt for the killings with the fall of the Iron Curtain, but its official investigation between 1990 and 2004 was broken off.
In last April's judgement, the Strasbourg court concluded that the killings constituted “a war crime,” and that several of the applicants had suffered “inhumane treatment” by Russian authorities.
However, the seven-member chamber was split over whether the court was able to rule on the adequacy of Russia's investigation, because the European Convention on Human Rights only came into force in Russia in 1998, eight years after Russia's Katyn investigation began.
The Chamber ultimately concluded that it was not able to rule on the matter, although the Polish legal team is hoping that the Grand Chamber will be of a different opinion.
Following today's public hearing, the judges deliberations will be carried out behind closed doors.
Other issues that will be resolved include the question of compensation.
When the case was initially filed in 2007, the Poles stated that they would forego compensation, save for a symbolic euro.
However, when more families joined the case, various claims for more substantial compensation were made.
Meanwhile, the Poles were displeased with the April ruling that only 10 of the 15 had suffered inhumane treatment at the hands of Russian authorities in their long-running bids to find out what had happened to their relatives.
The court ruled that “inhumane treatment” was not applicable to the remaining five, as they had no personal recollections of the deceased, even though once again, some were children of the murdered prisoners of war.
The complainants are being backed by Polish government, as well as several NGOs, including Russian human rights group Memorial and Amnesty International. (nh)