A police officer is under criminal investigation after footage showed him apparently physically restraining a man around the neck during an arrest.
A video, shared on social media, showed the man being restrained by officers on Spring Hall Lane, Halifax on 16 August.
The officer was suspended and an inquiry started by the Independent Office for Police Conduct (IOPC).
The IOPC said the West Yorkshire Police officer was now subject to a criminal and gross misconduct investigation.
During the video, a voice can be heard saying "chill out or I'll choke you out, chill out or you're going to sleep".
The incident sparked protests outside Halifax Police Station.
IOPC regional director Miranda Biddle said: "Having examined a range of evidence including body-worn video and initial accounts from the officers involved in the restraint, we have taken the decision that this is now a criminal investigation.
"A criminal investigation does not mean that criminal charges will necessarily follow."