Mijailo Mijailovic, a 25-year-old Swede of Yugoslav origin, confessed Tuesday while being interrogated by police and investigators, his lawyer, Peter Althin, told The Associated Press.
In an interview with Swedish radio, Althin said Lindh's stabbing wasn't political but didn't give a motive. When asked if it was a random act, Althin said, "You could say that."
"I do not have the written version of the interrogation in front of me so I cannot go into any details, but I can say as much as that there is no political motive," Althin said.
Mijailovic likely faces 10 years to life in prison, but could be sentenced to a mental hospital. Sweden doesn't have capital punishment.
The 46-year-old Lindh was stabbed several times in a Stockholm department store while she was shopping with a friend Sept. 10. Doctors worked for several hours to try to save Lindh, but she died the next morning.
Her death plunged Sweden into mourning and drew comparisons to the murder of Prime Minister Olof Palme, who was killed while walking home from a movie in 1986 in a slaying that has never been solved. Like Palme, Lindh had no bodyguards with her.
Mijailovic, who has previous convictions for assault, illegal weapons possession and making death threats, was taken into custody Sept. 24, and had originally said he was innocent.
Chief prosecutor Agneta Blidberg said the confession would likely result in a swifter trial.
"It is very possible because we had planned to cite witnesses, which means that the trial will probably be a few days shorter than we had planned," she told the AP. Initially, the trial was expected to last about six days.
Blidberg said that Mijailovic could be charged with Lindh's murder as early as Jan. 12.
Chief District Court Judge Goeran Nilsson said the trial could begin as early as Jan. 14 and could be over by the weekend.
"Mijailovic's confession should mean that the main hearing will be shorter than expected," he told AP. "Now, the prosecutors don't have to put all their evidence to the court."
Nilsson said he hasn't decided if Mijailovic should undergo a pretrial psychiatric examination.
Blidberg has said that DNA traces found on the knife used to stab Lindh matches Mijailovic's.
Justice Minister Thomas Bodstroen said the confession should give Swedes peace of mind that the right man was caught.
"If the suspect had been sentenced without having confessed, this could have led to years of speculation about whether the right person was sentenced," he said. "This can be avoided now."
Lindh, touted as a future prime minister of the Scandinavian country of 9 million, was popular with many Swedes. Her death shocked the country just days ahead of a national referendum on whether to adopt the euro, which failed.
By Matt Moore