Zaur Dadayev, the suspected triggerman in the Boris Nemtsov murder case, has been declared sane, the Kommersant newspaper reported on Tuesday.
Psychiatrists were asked to examine Dadayev in order to determine whether he was a religious zealot.
One theory in the case holds that Dadayev and his alleged co-conspirators killed Nemtsov based on statements of support he made after several members of the staff of French satirical weekly Charlie Hebdo were killed in January over their publication's propensity to publish comics of the Muslim prophet Muhammad.
Another theory is that the Nemtsov killing was motivated by cash or some other material reward.
Nemtsov, one of the Kremlin's most vociferous critics, was brazenly gunned down in the center of Moscow in late February. The murder shocked Russian society and was widely interpreted as a sign of a deterioration of the country's political atmosphere.
Dadayev, who is suspected of having pulled the trigger, initially confessed to his involvement in the killing, but later revoked his confession, claiming it had been made under duress.
In all, five people have been detained as part of the investigation.