Koptsev, who was 20 at the time of the attack, was given a 13-year prison sentence in March for the attempted murder of nine men on January 11, but was cleared of race hate charges, a decision that was later appealed by prosecutors.
"I deeply regret what happened and apologize to the victims' relatives for damaging their health," Koptsev told the court.
He continued, however, to maintain his innocence.
"I admit that I hurt nine people, but I cannot admit that this was based on racial hatred," Koptsev said, adding that he only wanted to injure the victims, not kill them.
"If I had wanted to kill them, I would have brought ammunition from home, or made some incendiary device," he said.
The contradictory testimony that Koptsev gave in court and during the preliminary investigation, had led the prosecutor to request that the interrogation transcripts be released.
Preliminary investigation established that he had operated alone, and did not belong to any extremist group.
Following his conviction in March, Russia's Supreme Court overturned the lower court's decision in June and ordered a retrial after both Koptsev's lawyers and the prosecutors appealed against the verdict.
In their appeals, Koptsev's lawyers said the defendant was mentally unstable, while prosecutors said a 13-year sentence was insufficient, and pressed for a 16-year sentence.
On July 31, the Moscow City Court refused a trial by jury for Koptsev and ruled that he be kept in custody for three more months.
The court session adjourned Thursday until August 31 when it will hear the arguments from both sides.
"Next Thursday, it will become clear what sentence the prosecutor is seeking for Alexander Koptsev," a court spokesperson said.
"The defense is also expected to put forward its arguments. Then the court will hear the last word from the defendant and adjourn to form a verdict."
On Thursday, the court also questioned two medical experts who confirmed previous psychiatric tests that had diagnosed Koptsev with a schizophrenic disorder. The experts concluded that the defendant had not been entirely sane at the time of the attack.
"He could not fully control his emotions and behavior, but was able to assess his actions and their significance," doctors said.
