Luciano Aviello's testimony Friday at an appeals court marks the latest flip-flop by the convicted Mafioso.
Aviello testified previously that his brother killed Meredith Kercher in 2007, but later recanted. Neither the defense nor the prosecution view Aviello's testimony as reliable, but Italy's highest court said it should be revisited at the new appeals trial.
Knox and co-defendant Raffaele Sollecito were convicted in the murder, and then acquitted on appeal in 2011. Knox, who went home a free woman after her acquittal, hasn't returned to Italy for her third trial.