Chicago's City Council has approved a $2.5 million settlement in an excessive-force lawsuit that accuses police of traumatizing a three-year-old girl by pointing a gun at her chest and striking her handcuffed mother.

A 2017 Justice Department report criticized Chicago police for too often using excessive force, including against children. The city has since pledged to overhaul police procedures and training.

A lawyer for Aretha Simmons, the girl's mother, says some police departments in other US cities have embraced far-reaching reforms on how officers should interact with children.

Attorney Al Hofeld Jr says a key element is for officers to recognize that the brains of small children and teenagers process information differently than those of adults.

Hofeld says upcoming Chicago Police Department reforms don't address how officers treat children during arrests.

A city lawyer told the committee the girl remains traumatised and will likely require psychiatric treatment into adulthood.