SEOUL - South Korea's top court upheld on Thursday a not-guilty verdict for the chairman of Samsung Electronics Jay Y. Lee, backing two lower court rulings clearing him of accounting fraud and stock manipulation related to an $8 billion merger in 2015.

The Supreme Court's verdict permanently removes a long-running legal distraction for Lee as Samsung plays catch-up in a global race to develop cutting-edge AI chips.

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The Supreme Court upheld an appeals court's ruling dismissing all the charges in the case involving the merger a decade ago between two Samsung affiliates, Samsung C&T and Cheil Industries, which prosecutors said was designed to cement Lee's control of the tech giant.

A lower court last year had also cleared Lee of the charges.

Samsung's lawyers said they were "sincerely grateful" to the court for its decision and added in a statement that the ruling confirmed that the merger was legal.

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Samsung Electronics shares were little changed after the ruling, up 1.7 percent.

The Supreme Court ruling was widely expected, but comes at a critical moment for Lee, who has faced mounting questions about his ability to lead Samsung Electronics - the world's top memory chip and smartphone maker - as it grapples with growing competition and playing catch-up in artificial intelligence chips. For nearly a decade, Lee has faced legal challenges, including those from the merger that paved the way for his succession after his father, Lee Kun-hee, had a heart attack in 2014 that left him in a coma.