Five police officers from four forces will face disciplinary procedures after separate investigations by a watchdog into social media messages related to Wayne Couzens, the killer of Sarah Everard.

They include two officers from the Metropolitan police – the force in which Couzens was serving at the time of the killing in March – who were questioned in the first of two investigations by the Independent Office for Police Conduct (IOPC).

The second investigation looked at allegations that seven officers from several forces breached standards of professional behaviour when they used the messaging platform Signal to share information connected to Couzens’ prosecution.

The watchdog said the allegations involved in the two investigations, if proven, “have the capacity to further undermine public confidence in policing”.

In the first case, a graphic shared by a Met probationary constable on WhatsApp was found by investigators to have been a reference to Evererd’s kidnap. The officer was off duty at the time but went on to staff a cordon as part of the search for Everard, the IOPC said.

“The image was highly offensive and the officer now has a case to answer for misconduct for potentially breaching standards of professional behaviour for conduct and authority, respect and courtesy,” the watchdog said.

It also found that one other probationary constable had a case to answer for misconduct for allegedly sharing the graphic and failing to challenge it. It said another constable did not have a case to answer for misconduct but would undergo “reflective practice”. This was on the basis that while they thought the graphic was inappropriate, they sought advice by forwarding it to two people rather than reporting it.

The investigation, which was completed in August, was launched after a referral from the Met in March. The IOPC said the graphic was challenged by colleagues and reported internally.

The deputy assistant commissioner Bas Javid, of the Met’s directorate of professionalism said: “The content of the graphic shared was incredibly inappropriate at an already distressing time, especially of course for Sarah’s family. The actions of the two officers who shared it were very disappointing, falling far below the high standards we strive to uphold in the [force].”

Following the second investigation, the IOPC concluded that an officer from Dorset police has a case to answer for gross misconduct after they were alleged to have posted details on 13 March of an interview given by Couzens under caution. The details were presented during a non-reportable court hearing several months before Couzens admitted murdering Everard.

Investigators looked at whether the messages, had they got into the public domain, would have brought discredit on the police service and potentially interfered with the course of justice. They also considered whether there was a legitimate policing purpose in sharing the information.

Dorset police will organise a gross misconduct hearing for the officer, who was on secondment from the force, for potential breaches of professional standards of behaviour relating to confidentiality, conduct, and challenging and reporting improper behaviour.

Evidence gathered during the six-month investigation also indicated that officers from other forces had joined in with the conversation, endorsing comments made by others and making unprofessional remarks about Couzens.

Two officers, from Sussex police and Avon and Somerset Constabulary, were found to have a case to answer for misconduct. In the case of the Sussex officer, they also allegedly breached standards for challenging and reporting improper behaviour.

At a meeting held this week for the Sussex officer, misconduct was not proven but the officer will undergo a “reflective practice” review in respect of one of the messages sent and the tone of conversation.

The IOPC’s investigation found no case to answer for a further four officers who were members of the chat group.

The watchdog is continuing to investigate the conduct of five officers from three forces and one former officer who allegedly sent discriminatory messages as part of a WhatsApp group between March and October 2019. They were recovered from an old mobile phone discovered during the investigation of Everard’s murder.

Other investigations are looking at how allegations of indecent exposure that have been linked to Couzens were handled by Kent police in 2015 and the Met in 2021.