Detective Chief Inspector Chris Jones attended the scene of Yorkshire student Anthony Walgate’s death in Barking, east London, on June 19 2014.
Having classified it as as “unexplained” rather than “suspicious”, he determined the case should be dealt with by borough officers rather than his specialist homicide team.
However, Mr Jones was not aware at the time of “inconsistencies” around the time of death or that the man who called 999 was a suspected rapist.
Giving evidence at the inquests into Port’s four victims, Mr Jones, who has since retired, denied there was “bias” because Mr Walgate, who was originally from Hull, was a young gay man and his death potentially involved drugs.
He said: “I cannot accept for one minute there is any bias in the approach to the investigation into the death of Anthony Walgate. You are alluding to unconscious bias. I have reflected on that. I have challenged myself. I am absolutely content that that does not exist in the way I approach any investigation.”
Mr Walgate, 23, had been found propped up against a wall outside Port’s flat in Barking, east London.
After making an anonymous 999 call just after 4am, Port claimed to police that the victim had “gurgled” before he moved him.
But medics called to the scene noted the body was cold and stiff, suggesting he had been dead for up to eight hours, the inquest heard.
In the course of identifying the caller, officers discovered Port had an allegation of rape recorded against him on the Police National Computer (PNC).
Andrew O’Connor, QC, counsel for the coroner, added that Mr Walgate had no mobile phone or wallet on him and had been “propped” up in a strange position.
He asked Mr Jones: “If you had been made aware of an inconsistency, Anthony ‘gurgling’ at 4am, and information from the ambulance man and doctor suggesting that could not have been right… Would that have altered your view?”
Mr Jones replied: “I think if a view had been expressed that the time of death had been prior or significantly prior to what is being presented by Stephen Port then that would be incredibly important.
“I think it is likely the death would have remained unexplained but the profile of Stephen Port would have been raised and specific questions around time of death could have been taken into the special post-mortem process.”
Mr Jones added it would have been “helpful” to have been told of the previous allegation of rape against Port when he attended the scene on June 19.
One of the officers recorded there was “nothing to suggest the victim had been assaulted”, despite bruising under Mr Walgate’s arms.
Mr Jones agreed that had been “wrong”.
The witness was asked about a request later in June 2014 for the case to be taken over from borough officers – which was refused.
In an email setting out the argument, a senior borough officer wrote that Mr Walgate “died at the hands of another” on the balance of probabilities.
Mr O’Connor said: “There is evidence Stephen Port had not only found the body on the Thursday morning but he had actually arranged to meet Anthony two days earlier and that he had withheld information.
“And there is evidence that he had a previous allegation of rape.
“Both those matters were known to you by then. Don’t those matters amount to a reason to classify this case as suspicious and therefore HAT (homicide assessment team) to take primacy?”
Mr Jones replied: “The conduct of Stephen Port was concerning but it was still my view that on the information I knew from the scene, from the post-mortem, that the matter did not cross the threshold for transferring to the homicide command.”
Mr O’Connor asked whether the decision gave borough officers the impression it did not need to be investigated any more as a possible homicide.
The witness replied: “Quite simply, no. Clearly the investigation was in full swing and I was no longer part of the investigation.
“That was an unexplained death in my mind – I appreciate what time has now shown. An unexplained death needs explaining.”
He added: “Nobody ever created the impression this is not a homicide investigation. This is not correct.”
Mr Jones was shown British Transport Police intelligence on an incident on June 4 2014, before Mr Walgate died.
It detailed a report that Port was seen going through a bag belonging to an “extremely ill” man.
Port claimed he found the man outside his house, thought he had taken “meth or G” (GHB) and he was looking through the bag to find his phone.
Mr Jones told jurors that had he known of the “impactive” report, his team would have taken over primacy.
However, he stood by his decision, based on what he knew at the time.
Between June 2014 and September 2015, Port gave all four of his victims fatal doses of the date rape drug GHB before dumping the bodies metres from his flat.
Port was later convicted of lying to police about the circumstances of Mr Walgate’s death, but not before he killed Gabriel Kovari, 22, and Daniel Whitworth, 21.
The killing spree was not stopped after until after the death of Jack Taylor, 25.
In 2016, Port was found guilty of the murders and handed a whole life order.
The jury inquest at Barking Town Hall is examining the competence and adequacy of the police investigation and whether Port could have been caught sooner and lives saved.