Sergeant Mark Andrews was caught on CCTV dragging Pamela Somerville, 59, across the floor of Melksham police station in Wiltshire before shoving her into the cell.
The officer was jailed for six months in September by a district judge at Oxford Magistrates' Court who condemned him for abusing a position of trust.
Sgt Andrews spent six days behind bars before he was released on bail pending an appeal against his conviction and sentence.
At Oxford Crown Court today his conviction and sentence for assault causing actual bodily harm were quashed by the appeal judge, Mr Justice Bean.
He said that after the four-day hearing he was satisfied that Sgt Andrews did not intend to throw Ms Somerville into the cell and that injuries she suffered were probably caused by her falling to the floor after letting go of the door frame. Ms Somerville needed stitches to a gash above her eye following the attack in July 2008.
She had been detained for failing to provide a sample for a breath test after being found asleep in her car, but denied any wrongdoing.
The charges were later dropped due to insufficient evidence.
Sgt Andrews, who is married with children aged four and two, joined Wiltshire Police around eight years ago and was promoted to sergeant in 2005.
Before joining the police, he spent around nine years in the Army, reaching the rank of sergeant.
In a statement issued after the hearing, Wiltshire Police said Sgt Andrews would remain suspended on full pay until the conclusion of an internal inquiry headed by another force.
Assistant Chief Constable Patrick Geenty said: "Whilst respecting the decision of the court today in upholding the appeal of Sgt Andrews the force has decided that it is appropriate for an independent force to hold an internal conduct hearing in early December which will examine the conduct of Sgt Andrews in respect of his dealings with Pamela Somerville throughout this incident.
"Due to the public interest and high profile nature of this case the result of that hearing will be made public.
"Sgt Andrews will remain suspended from duty until the conduct hearing and in accordance with national police regulations he will continue to receive full pay for as long as he remains a member of the force."
Mr Geenty said Wiltshire Police was "very concerned" when anyone was injured while in custody.
"In this case the court has decided that the injury to Pamela was not as a result of any criminal assault by Sgt Andrews," he said.
"Mrs Somerville had been found in her car suffering from the effects of alcohol and she refused a breath test.
"She was lawfully arrested for refusing the breath test and taken to the custody suite at Melksham where it is evident that she was very unco-operative, verbally abusive and disruptive to the processes which staff were required to carry out by law.
"It is appropriate to remind the public that this incident was reported by another police officer who was concerned at what had taken place.
"The officer found herself in a very difficult situation and, in spite of the decision today, she rightly reported her concerns and performed her duty in accordance with the highest standards expected of a police officer.
"The public will understand that the environment within custody centres can be very difficult with hostility, conflict and violence towards staff often occurring.
"Whilst these conditions can never excuse or condone any form of unacceptable behaviour by police officers or police staff, it is important to put this difficult job performed on behalf of the public and this isolated incident into context."
Mr Geenty said that often when officers dealt with "non-compliant" prisoners - people suffering from the effects of alcohol or drugs - there was often a need to use reasonable and proportionate force.
"Our staff have to make quick decisions there and then without the benefit of hindsight, but ultimately it is right that the judge of what is reasonable or unreasonable is for the courts and the decision today is that the force used was not unlawful," Mr Geenty said.
"During the two-year period between when this incident occurred and the original trial of Sgt Andrews, in excess of 30,000 people had been dealt with in custody centres in Wiltshire.
"During that period there were no other serious assaults of this nature and although there were a total of 13 complaints of assault, none were substantiated following thorough investigation."
He added: "Although this appeal hearing has concluded that no criminal offences had been committed, we are determined to learn any lessons that emerge from this case and we welcome the fact that the Wiltshire Police Authority has commenced its own independent review of our custody practices.
"We will not shirk from our responsibility to continue to ensure that we provide a professional service to the public."
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