How 1992 riots changed LA police
21 August 2014 Last updated at 06:37 BST
The shooting of unarmed black teenager Michael Brown in Ferguson, Missouri, sparked 10 nights of violent clashes between police and demonstrators.
Police arrested 47 people during protesters on Tuesday night, but said the violence had largely abated.
Such standoffs are not new, with the scenes in Missouri reminiscent of Los Angeles in 1992.
The BBC's Alastair Leithead reports on how the police force changed after the riots there, and what Missouri can learn from its experience.