The son of Randy and Gloria Johnson attended Sulligent High School and starred in football, basketball and track for the Blue Devils.

In spring practice of his sophomore season, he was told by coaches that he'd never be a starting running back there, but they wanted him to switch to defense and play safety.

That season (2006), he played in 11 games (missing two due to an ankle injury), starting four at free safety, and earned a full scholarship.

[5] In his junior year in 2007, the now-team captain started all 13 games and led the Tide with 81 tackles and six interceptions.

He earned Alabama Co-Defensive Player of the Year honors, was a first-team coaches' All-Southeastern Conference (SEC) selection, and earned shared UA's 2008 Mal Moore Leadership Award (with center Antoine Caldwell) for his performance during spring practice.

In the 2008 game versus LSU, Johnson had three interceptions (tying an Alabama single-game record), including one that he returned for a touchdown, and one in overtime that helped Alabama win the game and secure the SEC West Division crown.

[12] During a game against the New Orleans Saints on September 22, 2013, he lost his left middle fingertip.