Eriksson said that he did not fear losing a part of his soul, as Geir Lippestad, the lawyer who defending the Norwegian terrorist mass murderer Anders Breivik, claimed happened in his 2012 trial.
"A good way to deal with the case is to think of it as any other case. I've been defending people who have been having sex with their own children, killing people, doing things you won't imagine," Eriksson said.
"I don't defend the crime, I defend the man behind the crime. You have to deal with it as a criminal lawyer does."
Eriksson told Radio Sweden why he was happy to defend someone who a lot of people may believe deserves no defence at all.
"It's a test of the legal system because everybody hates this guy," he said. "It's a very important to test to show that the system can take care of cases like this."
He said Norway's handling of the Breivik case had been an inspiration to him.
Uzbek citizen Rakhmat Akilov has already confessed to driving the truck which this month drove down a busy shopping street in central Stockholm, killing four people, and also admited that he intended to commit a terrorist act.