Bank manager Alistair Wilson, 30, was involved in a planning wrangle over decking at the Havelock Hotel in Nairn, which sits yards from the murder scene.
The father-of-two had objected to a retrospective application for the decking, which he insisted increased noise and litter levels.
Mr Wilson’s objection is being treated as significant to the enquiry and officers have flown to Canada to interview an expat Scot who was landlord of the hotel at the time.
Detectives believe his stance was discussed in the hotel bar on Friday, November 26, 2004, and over the weekend up until Alistair’s murder on the Sunday night.
IDetective Superintendent Graeme Mackie, of Police Scotland’s Major Investigation Team, said: “This would have been the first time Alistair’s objection to a retrospective planning application for the decking would have become public knowledge.
“We want to know what was being said about it and who else was there as this may be significant to our investigation. I would ask anyone with information, no matter how insignificant they think it might be, to please come forward.”
Mr Wilson was shot around 7pm after a man called at the family’s home on Crescent Road, spoke to his wife Veronica and asked for her husband by name.
He went downstairs to speak to the man and was handed a blue envelope with the word “Paul” on it. He went inside briefly and then returned to the door for a second time when he was fatally shot.
Last month detectives interviewed a key witness in Canada regarding the planning application and believe the answer to the murder lies within his personal life and is not connected to his employment with the Bank of Scotland.
Police Scotland also issued an appeal for information about two men seen with a handgun on a beach near the town a month before Alistair’s murder.
The gun used in the murder, a Haenel Schmeisser, a 1920s German handgun known as a pocket pistol because of its small size, was found down a drain in Nairn days after the shooting.