A Gwent Police officer has been sacked for striking a detainee three times in the chest with his knee.
PC Callum Powell breached of professional standards in use of force on Fathal Moshen, a misconduct hearing in Cwmbran, Torfaen heard.
He had claimed to be "within his rights" telling a previous hearing Mr Moshen posed a "real viable threat".
But the panel concluded his conduct was discreditable and amounted to gross misconduct.
Christopher Mckay, the legal chair of the panel, said: "It must be made clear to other serving officers that they will face the most severe of outcomes if they treat a detainee in custody this way.
"Therefore, the only outcome is dismissal without notice."
Moshen's mother, Ahman Kassim, said she was happy with the sacking of PC Powell, who had served on the force for seven years.
"It's taken a long time to get here," she said after the hearing. "It's the right decision by the panel for what he did to my son while he was in custody, in handcuffs with his hands behind his back.
"It has traumatised me seeing that video of what happened in the cell."
Use of force 'disproportionate'
The hearing was shown CCTV footage from Newport Central police station in July 2021 wherein PC Powell can be seen striking Mr Moshen in the chest with his knee three times.
He was attempting to put a spit hood over the detainee's head in a custody cell, but had been resisted several times.
Mr Mckay found a "loss of control and temper" in the officer's handling of Mr Moshen.
Mr McKay said, "It is likely Mr Moshen suffered bruising from the assault.
"Even though Mr Moshen had been difficult and uncooperative in custody, insulting and spitting at PC Powell, the officer abused his position of power.
"He held the detainee's arm up and bent it backwards while he struck him three times in the chest with his knee.
"The use of force was disproportionate and inappropriate. And was liable to cause reputational damage to Gwent Police," added Mr McKay.
Dept Ch Con Rachel Williams, said: "The behaviour of Calum Powell fell significantly below the high standards that we require of all our officers and staff, and today he has been held to account for his actions.
"The level of force he used was excessive and completely unacceptable. There is no place for this type of behaviour in Gwent Police.
"Behaviour such as this only serves to undermine the committed work of the vast majority of police officers and staff who work tirelessly to protect the public with dignity and courage every day.
"At Gwent Police, we are fully committed to ensuring inappropriate behaviour is rooted out and we will continue to robustly investigate those whose behaviour falls below the high standards that we and our communities expect."