He wasn't convicted because the prosecution couldn't find a witness that could testify they saw Lewis stabbing the victim. But there were plenty of witnesses who verified that Lewis was present. Plus, they had him on obstruction of justice, aiding and abetting, and probably accessory to murder.
Ultimately, the prosecutors gave Ray a deal he couldn't refuse.
“On the offense last year, they had great spacing. That’s what I remember. Great spacing, great shooters, like Nik Stauskas, who’s not there right now. But they always have someone to fill the roles. They have a cutting offense, kind of hard to guard.”