Judge Cahill also denied motions to dismiss charges against the other three officers involved — Tou Thao, Thomas Lane and J. Alexander Kueng — who remain accused of aiding and abetting the killing.
Explaining his decision in a 107-page ruling, the judge said the third-degree charge did not stand up because there was no proof Chauvin put anyone else in danger during the ill-fated arrest in May.
"Under Minnesota law, a person is guilty of third-degree murder if 'without intent to effect the death of any person, [the defendant] causes the death of another by perpetrating an act eminently dangerous to others and evincing a depraved mind, without regard for human life'," he wrote.
To prove Chauvin is technically guilty of third-degree murder, the state must prove three things: That Floyd actually died, that Chauvin caused Floyd's death, and that "Chauvin's intentional conduct that caused Floyd's death was performed without regard for human life."
"Such an act may not have been specifically intended to cause death, and may not have been specifically directed at the particular person whose death occurred, but it must have been committed in a reckless or wanton manner with the knowledge that someone may be killed and with a heedless disregard of that happening," he added.
The state has five days to appeal the ruling.
The court has sustained 8 out of 9 charges against defendants in the murder of George Floyd, incl the most serious ones. All 4 defendants will stand trial for murder & manslaughter in the 2nd degree. This is a positive step fwd in the path to justice. https://t.co/kIDsqm1zN3
Minnesota Attorney General Keith Ellison said the court's decision was "an important, positive step forward in the path toward justice for George Floyd, his family, our community, and Minnesota."
"The court has sustained eight out of nine charges against the defendants in the murder of George Floyd, including the most serious charges against all four defendants," he wrote. "This means that all four defendants will stand trial for murder and manslaughter, both in the second degree."
On May 25, Floyd died on the pavement outside a store he was accused of using a fake $20 in, begging for breath, as Chauvin knelt on his neck for almost nine minutes.