TMZ Sports has obtained police video from Justin Layne's arrest Friday ... and the Steelers DB can be heard in the back of a squad car saying, "They acting like I got some drugs -- I got one blunt!"
The 23-year-old -- who was a Steelers third-round pick in 2019 -- was pulled over after cops say he was doing 89 MPH in a 60 MPH zone in his 2020 Dodge Charger.
During the stop, officers put him in the back of a patrol car while they searched his ride ... and that's when Layne got on the phone with some of his friends to talk them through his situation.