Officers investigating the death of Sheku Bayoh considered whether the case could be linked to terrorism, an inquiry has heard.

Detective Chief Superintendent Pat Campbell said he initially considered various hypotheses which could have led to the death of Sheku Bayoh, including that it could be linked to the restraint by officers, or could be due to an underlying medical condition.

He said the idea of a potential terrorism link was “quickly eliminated” after background checks, but that investigating various hypotheses was part of keeping an open mind during the inquiry.

Mr Bayoh, 31, a father-of-two, died after he was restrained on the ground by six police officers in Kirkcaldy, Fife, on May 3 2015.

The inquiry is investigating the circumstances of his death and whether race was a factor.

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Mr Campbell, who was a detective superintendent at the time, said he came up with a number of theories as he drove to Kirkcaldy on May 3 after being appointed senior investigating officer (SIO) to the incident.

Angela Grahame KC, lead counsel to the inquiry, asked why he considered the terrorism-related idea as a hypothesis in the first place.

Mr Campbell said: “It was really the circumstances of the incident. What we had was a male with a knife at six o’clock in the morning in a relatively quiet town, Kirkcaldy, acting erratically.

“So again, that was not the initial focus, that was just one of the hypotheses as I say, just to keep it extremely open and transparent that we were looking at absolutely everything that we could basically consider to ensure that there was rationale and accountability around my decision-making around that.

“But as I say, it was only one aspect of it, but with the necessary checks that we carried out through our intelligence side we could quite clearly identify that there was no aspect of terror-related motivation around this.”

He said the climate in relation to threats to police was also different in 2015, when the threat level was classed as “severe” and the risk of an attack on officers was thought to be highly likely.

Mr Campbell, giving evidence on Thursday, said that the consideration of terrorism as a hypothesis was not linked to the colour of Mr Bayoh’s skin.

Ms Grahame said: “You’ve not mentioned the fact that Mr Bayoh was black, was that one of the factors?”

He replied: “No, absolutely not, if it was a white male with a knife restrained by police officers I would still have had the same hypotheses around let’s get the checks done, is he linked to any particular aspect of the terror network as such around that. So Mr Bayoh being black had no relevance at all to it.”

The lawyer asked: “So if it had been a white male involved in those circumstances, would counter-terrorism checks have still been carried out?”

He replied: “Absolutely”.

Mr Campbell said that the other hypotheses he had considered were whether Mr Bayoh’s death could be linked to drugs or drink, or an earlier assault which may have led him to Hayfield Road.

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He said that during the time he was SIO, he could not eliminate the hypothesis that restraint could have been a factor in Mr Bayoh’s death.

The police officer told the inquiry: “That was one I ran with during the time I was SIO and through the inquiry that I was unable to eliminate at that time, that restraint was a potential contributory factor to the death of Mr Bayoh.”

Mr Campbell also told the inquiry that he felt some trepidation about handing the incident over to the Police Investigations and Review Commissioner (Pirc) team, which arrived in Kirkcaldy at about 1.25pm on May 3 and took over as lead investigator, having been managing it remotely since around 9.30am that day.

He said that police had around 22 detectives involved while Pirc arrived with a team of four or five and he had concerns about Pirc’s capabilities with those resources.

Mr Campbell said: “There was a reluctance perhaps on my part to relinquish control of the incident due to the fact that I was conscious that it was moving at pace and I believed in the right direction at that stage, so there was a bit of trepidation round about, would it set it back, the investigation, if we did a complete handover at that particular time.”

The inquiry, taking place before Lord Bracadale in Edinburgh, continues.