"One must be aware that serious mental illness is a mitigating factor," said a lawyer for Frank S., the 44-year-old man accused of trying to kill Cologne's mayor Henriette Reker last year.

Wednesday's closing arguments at a Düsseldorf court saw defense attorneys plead for a 15-year sentence, instead of the lifelong prison term sought by prosecutors.

The defendant said that "the evidence has been crudely manipulated and in some cases invented," to make it look like he was a cold-blooded, premeditating would-be murderer.

Reker was stabbed in the neck the day before the October 18, 2015 elections, which she won by a margin of 52.66 percent. While Frank S. has since told the court that his knife was blunt and that he did not intend to actually kill her, this contradicted statements he made to the police in the initial aftermath of the attack.

As a member of city government before her mayoral campaign, Reker had been in charge of social affairs and the integration of refugees for Cologne, and multiple witnesses confirmed that her attacker made xenophobic statements as he went to stab her. Four bystanders were also injured in the fracas.

Reker won the election while in the intensive care unit of an area hospital. She later said she was terrified she would be paralyzed, as the blade reached all the way to her spine.

Former neo-Nazi

In the course of the trial, Frank S. has confirmed that the attack was politically motivated.

"I saw it as a final opportunity to change something," he said, after bemoaning the "self-destruction" Germany was engaging in by accepting so many refugees, some 1.1 million in 2015. One police officer told the court that the suspect admitted to a desire to kill Chancellor Angela Merkel as well immediately after his arrest.

During the proceedings, it emerged that S. had previously been active in far-right movements in Germany, and participated in a demonstration in honor of Adolf Hitler's Deputy Führer, Rudolf Hess, who killed himself in a West Berlin prison in 1987. The defendant has already spent three years in jail for assault charges stemming from an altercation with far-left activists.

In their own closing statements, the prosecution had suggested a life sentence for attempted murder and grievous bodily harm. The verdict is set to be delivered in early July.