Outlining the progress of the investigation, Detective Inspector Bobby Dow said: "A detailed forensic examination of the house in Murrayfield Gardens area, coupled with witness reports, has revealed that John was involved in a significant physical altercation within the property shortly before he was found dead in the street.
"Whilst we have returned the house to the occupier, our inquiries are continuing to establish exactly what happened the night of John's murder and who is responsible."
Police have reiterated their calls for anyone with information about what happened that night to contact them. "I would urge anyone who has knowledge of what took place in the house or who might be involved to get in touch with us," said Mr Dow.
"Establishing exactly what happened in that house is a significant part of our investigation and may be key to finding out who is responsible for John's murder. We continue to update John's family on the inquiry and they have been fully supportive of the investigation carried out so far. Someone knows who is responsible and can give John's family the answers they deserve."