Yury Dmitriev exposed mass killings carried out during Stalin’s era, but found himself at odds with the Kremlin narrative that Russia must not be ashamed of its past. He was cleared of the first round of child pornography charges in April by a court in the northwestern region, where Dmitriev heads Memorial, an independent NGO that investigates Soviet-era crimes.

A court has overturned the acquittal of a prominent Russian historian and civil rights activist on child pornography charges, sending the high-profile case back for a retrial.

The Karelia region’s supreme court annulled Dmitriev’s acquittal, which was originally handed down by a lower court, his lawyer Viktor Anufriyev told the 7x7 news website Thursday.

Anufriyev said Dmitriev's adopted daughter was pressured into telling psychiatrists she was upset, after which her grandmother appealed the not-guilty verdict. Experts in the original trial found that naked pictures of the child, which Dmitriev said were taken to monitor her health, were not pornographic in nature.

During his first trial, human rights groups said the charges against Dmitriev were politically motivated for his historical work.

Anufriyev told Agence France Presse that the Karelia supreme court’s decision was “unlawful and not based on criminal legislation.”

“[Dmitriev] takes this decision philosophically, he has experienced life and has seen even worse,” the lawyer was quoted as saying.

Reuters contributed reporting to this article.