Tire tracks were found at the crime scene. On Thursday, Hernandez's lawyer James Sultan asked Massachusetts State Police Trooper Timothy Dowd about tire pressure.
As he wrapped up cross-examination, Sultan asked one last question: ''Did you ever receive training in football deflation devices?''
Dowd said no, and Sultan sat down.
The Patriots were accused of using underinflated footballs in their AFC championship win. The NFL is investigating.
The team went on to win the Super Bowl.
Hernandez is accused of the 2013 killing of Odin Lloyd, who was dating the sister of his fiancee. He had a $40 million contract when he was arrested.