A policeman has been sacked for "unnecessary, disproportionate and unacceptable" behaviour by standing on a handcuffed man's head and kicking it.
PC Warren Potter, of Hertfordshire Police, had been responding to a call for assistance from colleagues who had detained a man in Hatfield in January.
A misconduct panel found he "failed to act with self-control".
His "gross misuse of force towards a vulnerable detainee" amounted to gross misconduct, the force said.
On 13 January, PC Potter responded to the call from colleagues dealing with a man, known as Mr JB.
The panel heard Mr JB had spat at another officer, was on the ground, handcuffed "to the rear" and was being restrained by four other officers.
'Significant potential for harm'
PC Potter's "right foot had been placed on Mr JB's head for a total of 24 seconds and that for two short moments most or all of his bodyweight had been directed through this right foot, including the point at which the officer used his left foot to deliver a kick to Mr JB's head", the panel heard.
PC Potter had "sought to justify his use of force", referencing the "threat of him spitting again" and he also claimed his belief that Mr JB had a contagious disease to be "relevant".
The panel said: "Notwithstanding that the person being arrested had been abusive and had spat towards a colleague, PC Potter's behaviour was deemed totally unnecessary, disproportionate and unacceptable.
"PC Potter failed to act with self-control, or tolerance, or treat Mr JB with respect his rights and vulnerability."
They also did not accept his explanation "as to why he had not subsequently completed a 'use of force form'".
The panel said Mr JB appeared to have suffered "minimal" physical harm, but the "potential for harm from the contact to his head was significant".