Teenager Pleads Guilty to Planning a Bombing at the Sydney Marathon Finish

A teenager has pleaded guilty to acts done in preparation for a terrorist act after researching a bombing at the Sydney Opera House on the day the Sydney Marathon finishes there, the New South Wales Supreme Court heard on Tuesday, two days after 40,000 runners set out for that finish line in the race’s second year as a World Marathon Major.

Australian Federal Police arrested the boy, who cannot be identified for legal reasons, at his home in western Sydney in August 2024, when he was 14, ABC News reported. He is 16 now. The court heard that his first exposure to extremist material came through TikTok that year, and that he later used Telegram, an encrypted messaging service, to discuss committing terrorism with people he met online.

The race in question in 2024 was a smaller event than the one Sydney staged on Sunday. The 2024 edition, held Sept. 15, drew a then-record 20,272 finishers, according to World Marathon Majors, which admitted Sydney to the series in November 2024, three months after the arrest. The first Major edition followed in 2025. This year, 40,000 runners entered the marathon and another 10,000 the Saturday 5K, Transport for NSW said before the weekend.

What the Court Heard About the Target

“I am picking the location, places where lots of people and tourists are out,” the boy told someone online, in a message he accepted as his own at the hearing, reported by AAP. He told the court that the marathon interested him because of the number of people the finish line brings to the Opera House, and that the site therefore offered the greatest potential loss of life. He also said he had been “50:50” about whether he would go through with it, and described a “little voice” in his head that warned him off, telling him the consequences would fall on his family.

According to court documents cited by ABC, he sought instructions for making a pressure cooker bomb and tried to contact the surviving perpetrator of the 2013 Boston Marathon bombing. On his computer, officers found upwards of 40 extremist videos.

Two pressure cooker bombs exploded near Boston’s finish line on Boylston Street on April 15, 2013. Three people were killed, and by the FBI’s count more than 500 were injured. The man who survived that attack, Dzhokhar Tsarnaev, was convicted on all 30 counts against him and sentenced to death in June 2015, according to the FBI. An appeals court set that sentence aside and the Supreme Court restored it in 2022. He was still challenging it on juror bias grounds in August 2025.

What the Sentence Could Look Like

His barrister, Michael Valentin, asked Justice Stephen Campbell for a non-custodial sentence so that the boy could continue his deradicalization in the community, and said he was “now out of the rabbit hole.” The boy apologized to the court: “I’m deeply sorry for the things I did.” Crown prosecutor Sophie Callan SC accepted that his evidence had been “candid” but argued that nothing short of a custodial term would be appropriate. “There remains a level of naivety in expressions of insight … that would leave Your Honour with a degree of caution,” she said.

The offense he has admitted carries a maximum penalty of life imprisonment. Head sentences in comparable cases involving offenders who were under 18, as listed in the NSW Public Defenders sentencing table for the charge, run from about 7 years to 16, with non-parole periods of roughly five to 12 years. In one case involving a wider conspiracy, a boy who was 14 at the time had his sentence cut on appeal to 10 years 9 months, with eight years to serve before parole.

Bail conditions imposed in November 2024 have kept the teenager at home, with outings his parents supervise, and he remains on bail. Campbell will sentence him on Oct. 29.