The Independent Police Complaints Commission (IPCC) has instructed Humberside Police to hold gross misconduct hearings for two police officers following an incident which occurred 17 years ago.
Following the death in custody of former paratrooper Christopher Alder, 37, in 1998, officers carried out surveillance on his sister Janet Alder and another person in 2000.
The IPCC investigation followed a referral by the force in August 2013 after the Home Secretary requested all forces check their records for evidence of surveillance as part of the inquiry into the death and investigation of Stephen Lawrence.
Humberside Police's searches revealed evidence of surveillance into Ms Alder and another person.
The IPCC investigation, which was completed in January 2015, found evidence of a case to answer for gross misconduct for two detective sergeants.
The report was referred to the CPS which concluded earlier this year there was not enough evidence to provide a realistic prospect of conviction against each defendant in relation to the surveillance carried out.
Humberside Police did not initially share the IPCC’s view regarding a gross misconduct hearing which led to IPCC Commissioner Cindy Butts writing to the force to direct it to hold hearings for the officers.
Ms Butts said: “The decision to direct a police force to hold disciplinary hearings is not taken lightly. Taking into account the serious and sensitive nature of the allegations and the weight of the evidence presented to me, I felt it was essential for public confidence that the officers concerned account for their actions.”
The IPCC will consider publishing its findings in full, once all proceedings have been concluded.
The dates for the hearings will be confirmed in due course.
Mr Alder died while lying face down and unconscious in a pool of blood in a police custody suite in Hull.
CCTV showed he received no help from five police officers who were nearby and thought he was play acting. It took 11 minutes for him to stop breathing.
Afterwards, as Mr Alder lay dead, monkey-like noises were detected on the audio tape.
After an inquest lasting seven weeks, a jury returned a verdict of unlawful killing, citing "positional asphyxia".
Five police officers were prosecuted for manslaughter but the trial was halted when the judge ruled there was no evidence for a conviction.
They were later cleared by a police disciplinary hearing of neglect of duty.