I watched the video. Looks to me that the woman was shielding her head with her arms, and the officer was not forming a fist, so the blows were combative but not destructive. If the woman had spat at the officer, it can constitute dangerous assault, if the saliva contains e.g. AIDs tainted blood. So it is possible the officer was using reasonable force. This one bears investigation, but the verdict is not a forgone conclusion.