STOCKHOLM, Feb 28 (Reuters) - Forty years after Prime Minister Olof Palme was shot dead on a Stockholm street, Swedes are still wondering whether the murder was the work of a lone gunman or a political assassination.
Decades later, the murder remains unsolved, and amateur detectives have turned to Artificial Intelligence in the hope of identifying new leads and persuading authorities to reopen an investigation that was shut down in 2020.
The team on a crime podcast called Spår ("Track") has started investigating leading theories about the murder with an AI engine developed for them by Swedish and Belgian software firms.
"This is about the murder of our leader, a democratically elected prime minister. You can't just close the case," said Anton Berg, a co-presenter of the podcast, which intends to present the findings using AI gradually.
So far, Spår has announced no breakthrough in the case. But, pointing to the ability of AI tools to learn and improve, Berg said: "Our hope is that this tool will get so advanced that we can open up the investigation again."
PARADIGM SHIFT
Palme was shot dead at close range on his way home from a visit to the cinema on February 28, 1986.
Over the years, the finger of blame has been pointed at South Africa's apartheid-era security services, Kurdish freedom fighters, right-wing extremists within the Swedish state and various lone gunmen.
One man was convicted, but later freed, and prosecutors closed the case in 2020. A review last year confirmed the case would remain shut despite the main suspect being absolved.
"We don't know any more than we knew on the day of the murder, essentially," said Gunnar Wall, who has written several books on the Palme killing.
On Saturday, the 40th anniversary of Palme's death, protesters will hand in a petition to parliament urging authorities to reopen the case. Such calls could get a boost if amateur sleuths are right in believing AI can now do what decades of police work failed to achieve.
The AI engine developed for the Spår crime podcast mimics a team of human investigators to probe evidence, evaluate findings and identify gaps, but can do so much more rapidly.
It can analyse the case's around 30,000 publicly available digital documents in less than a second. Otherwise the entire case files - about 500,000 pages - would take a decade just to read, police say.
From fingerprinting to DNA profiling, forensic technology has reshaped criminal investigations. AI could be another game-changer, experts say.
In 2018, AI-assisted DNA analysis helped Los Angeles police catch Joseph DeAngelo, known as the Golden State Killer, who had murdered 13 people and raped at least 50 people many years earlier.
"AI is a paradigm shift," said Lena Klasen, the former head of Sweden's National Forensic Centre and now Adjunct Professor in Digital Forensics at Linkoping University.
"It is going to change how we work in the way that computers did. But this is bigger."
CAN AI PROVIDE ANSWERS?
Swedish police declined to say whether they had used AI in the Palme case, which will not be reopened unless there is good reason to believe that an investigation would lead to an arrest and conviction.
Even with its data-crunching power, AI may struggle to find Palme's killer.
Case files are often heavily redacted and vast quantities of material is still unpublished, said Simon Lundell, part of a separate group of amateur investigators using AI in the hope of catching Palme's killer.
Gaining access to police files takes time, with only around 1,000 pages per year released. At this rate, it would take hundreds of years to be able to review all the information.
Despite such problems, "our goal is to solve the murder," Lundell said.
There is also no guarantee that the evidence needed to solve the Palme case even exists. Three public commissions concluded that police bungled the early investigation. Documents were lost and leads were not followed up.
"There is no technique that can help with information that isn't there, and that is a big part of the problem that there are gaps in the information," said Lennart Gune, Director of Prosecution at the Swedish Prosecution Authority.
The use of AI in investigations also comes with some concerns. The Golden State Killer case caused a fierce debate about privacy after millions of people had their DNA data scanned without their explicit consent.
In 2025, Sweden proposed a law that will allow police to use real-time, AI-powered face-recognition as a tool to fight gang crime, but its use will be limited over concerns about privacy and AI surveillance.
(Reporting by Simon Johnson, Editing by Timothy Heritage)
