The details of the incident and reprimand for the officer, whose name has been redacted, have been revealed through a decision notice following a recent misconduct hearing.
On Friday, December 13, 2024, while off duty on a work social night out, the officer acted inappropriately.
This was through approaching a younger female colleague, who was junior in rank, from behind and slapping her on her bottom without her consent.
He engaged in 'unwanted, offensive, and inappropriate behaviour that showed a lack of respect and courtesy, discrediting Cheshire Police and the police service as a whole, thereby impacting public trust and confidence in policing'.
The hearing was told the incident had been caught on CCTV, with the complainant immediately informing her colleagues the officer had 'slapped her a**e'.
Those colleagues spoke to the officer to warn him in relation to his behaviour, and he acknowledged and apologised for his behaviour.
Chief Constable Mark Roberts, presiding over the misconduct hearing, ruled the behaviour of the officer did breach the standards of professional behaviour, and it amounted to discreditable conduct and gross misconduct.
He ultimately considered a final written warning was the most appropriate sanction, taking account of all the circumstances of this case.
"I give considerable attention to the motivation behind this incident and viewed the CCTV numerous times," CC Roberts said.
"The officer denies a sexual motive, and this is a key factor in my considerations, and the appropriate authority did not pursue this issue.
"It is an important factor the officer was in an acting sergeant's role at the relevant time, and he is significantly older than the complainant - both factors that arguably create a power imbalance between them.
"Fortunately, in this instance, the complainant did have the courage to report this matter immediately to colleagues."
It was said the complainant's initial account was that she was upset by the slap, but she did not consider it sexually motivated.
A misconduct hearing took place at Cheshire Police's headquarters in Winsford
"Policing has come under national scrutiny through high-profile cases where there has been a failure to prevent or protect women and girls from abuse and violence, and when violence has been perpetrated by those serving the police," CC Roberts continued.
"It is imperative that policing makes it clear that misconduct of that nature is wholly unacceptable, setting a clear expectation as to the seriousness with which those matters are treated.
"In his response, the officer accepted that the slap was unwanted and inappropriate, that the slap made the complainant upset, that his conduct engaged and breached the standards of professional behaviour, and that his conduct was unwanted and inappropriate.
"Given all of the current context and the need to maintain public confidence, and the confidence of our own staff, particularly females, the act in itself clearly amounts to gross misconduct."
He added: "The key factor in determining sanction was then to understand motivation.
"Was this an out-of-character moment of inappropriate stupidity set in a 22-year unblemished career, or an older male in a supervisory position, in drink at a social event, committing an act against a younger female officer?
"In terms of public confidence, and whether I and the force take violence against women and girls sufficiently seriously, I can point with confidence to our record over the last four years.
"Tackling violence against women and girls has been a priority for the force since I returned in 2021.
"Every misconduct hearing case thus far that has come before me, where violence against women and girls has been an issue, has resulted in dismissal.
"The officer in this case who received the slap has done absolutely the right thing in raising her concerns and is to be commended for doing so, but she herself stated she did not want the officer to lose his job.
"He has denied there was a sexual motive behind his action, there is no record of any similar incidents in a 22-year career, and it is to his credit that he has been at work while under investigation.
"There was no build-up to the incident, and it appears to be an isolated incident. No doubt this has been a difficult situation to manage at home, so it will be clear to him as to the gravity of his situation.
"All I have seen, read and heard suggests this was a one-off incident of stupidity.
"As such, I consider that the appropriate sanction will be a final written warning, lasting for a three-year period."