From Rolling Stone:
Singers Marley, Peter Tosh and Bunny Wailer saved some of their prettiest falsetto harmonies for one of the group’s toughest songs, and in the process they woke up white rock audiences to the sound of the Wailers and reggae. Inspired by the Impressions‘ “Keep On Pushin’,” Marley originally had the song’s outlaw hero say “I shot the police” but imagined the song would be more government-friendly if he changed it to the revenge killing of a single sheriff. U.S. rock radio warmed up to the song when Eric Clapton covered it, scoring a Number One hit in the summer of 1974.
From allmusic, reviewing the album:
“I Shot the Sheriff“…claims self-defense, admits consequences (“If I am guilty I will pay”), and emphasizes the isolated nature of the killing (“I didn’t shoot no deputy”), but its central image is violent. Such songs illuminated the desperation of poor Jamaican life, but they also looked forward to religious salvation, their themes accentuated by the compelling rhythms and the alternating vocals of the three singers.