US policeman 'seen hitting' woman in California
5 July 2014 Last updated at 16:29 BST
The California Highway Patrol says that it is investigating footage posted on YouTube that shows a policeman repeatedly punching the face and head of a prostrate woman.
Police say that the woman needed to be restrained and was endangering herself and motorists by walking on a busy road in the west of Los Angeles.
Chris Rogers reports.