This was stated in Russian authorities' responce to the questions asked by the ECHR.
Russian law enforcement authorities allegedly conducted a thorough investigation of Sentsov’s allegations of ill-treatment and found no reason to initiate criminal proceedings.
The Russian authorities explained the abrasions and bruises of Sentsov by the fact that during his arrest and search "he was briefly pressed to the wall".
Earlier, Sentsov's lawyers filed an appeal on behalf of the political prisoner, which said that the Russian authorities violated article 3 (prohibition of torture) and article 5 (right to liberty and security) of the Convention for the Protection of Human Rights and Fundamental Freedoms.
Oleh Sentsov and Oleksandr Kolchenko were detained in Crimea on May 10, 2014. They were sentenced to 20 and 10 years in prison, respectively, on charges of preparing terrorist attacks.