An investigation into the fatal shooting of an IRA man in Co Down more than 30 years ago has found a subsequent police inquiry "lacked independence and rigour".
The report found no evidence of a conspiracy, however, as had been alleged by the family.
Colum Marks was shot dead by a police officer in Downpatrick as the IRA prepared a mortar attack on the security forces in April 1991.
An intelligence-led operation had been mounted to thwart the attack and detain suspects.
A solicitor for the family said the report supported their belief that there had been sufficient time to effect an arrest.
Many of the records dealing with the operation have since been destroyed.
Officer B was the policeman who shot Colum Marks.
An investigation by Northern Ireland's Police Ombudsman found various issues with the subsequent RUC investigation including the fact that he was only asked five questions during his interview.
"Officer B's interview failed to adequately examine his actions or mindset at the time of the incident, and lacked the necessary depth and rigour expected in light of the fact that this was a fatal police shooting.
"Equally, the statements provided by other officers omitted critical detail about the planning, tasking, coordination and communications on the night.
"Significantly, they do not mention any briefings or information received prior to their deployment on this operation, including the suspects believed to be involved."
Radio transmission logs record that Colum Marks was seen carrying what appeared to be a mortar and was identified a short time later in the driveway of a house at St Patrick's Avenue where it had been assembled.
When he was challenged he ran across an adjoining recreation ground at which point he was shot.
An allegation that Colum Marks had been shot in the back was considered by the investigation team and experts who were commissioned to run tests on clothing and do a reconstruction.
The Police Ombudsman determined that a criminal offence may have been committed and forwarded a file of evidence to the Public Prosecution Service in 2021.
In May 2023, the PPS concluded that there was no reasonable prospect of a conviction of Police Officer B based on the evidence.
Police Ombudsman Marie Anderson found that the absence of records - particularly from the unit responsible for co-ordinating the security operation - had impeded her ability to assess whether there had been opportunities to arrest Mr Marks.
"There are no existing Tactical Co-ordinating Group (TCG) records and there are no witness statements or depositions from TCG officers explaining their role and participation in the planning and decision making.
"I am unable to conclude, therefore, whether there was an opportunity to disrupt the planned mortar attack, to arrest Mr Marks before that evening or to arrest him prior to the first recorded sighting of him by Police Officer B at 9.29pm.
"However, from the evidence which is available, there was a short window of opportunity to arrest Mr Marks on that evening between 9.29pm, when he was first observed carrying the mortar, and 9.47pm when the instruction was given to arrest him.
"It is clear that police intended to arrest suspects in circumstances that connected them to the weapon, and the intent to commit an unlawful act, rather than possession of the weapon alone.
"In the presence of what was described as a viable explosive device, it is my view that this was a high-risk strategy on the part of police whose primary duty was to protect life."
In a parallel investigation the ombudsman looked at allegations that Officer B had been asked to lie about elements of the investigation.
Officer B accepted that he had sent a text to a fellow officer to that effect, but said it related to the post incident debrief and other procedures which had not been carried out properly.
He said he had never been asked to lie about what happened on the night of the shooting.
"The investigation of complaints about historical matters is challenging due to the passage of time and unavailability of relevant witnesses and documentation," Police Ombudsman Marie Anderson said.
"In their complaint, the Marks’ family sought clarity as to the events of 10 April 1991. Regretfully there remain unanswered questions due to the absence of records and in particular information about the TCG operation.
"The effect of the practice of destruction of these records is that the TCG operation has not been subject to independent examination and scrutiny."
