Sandy Ingram was found lying outside his Newmachar home at 11pm on June 19, 2010 – moments after going outside to investigate a sighting of two men in his garden.
The farmer and his wife, Ann, had been sitting inside Elrick House, when Mrs Ingram spotted the intruders.
When Mr Ingram failed to return, Mrs Ingram went out to find him lying face down and unconscious.
A description of the two men was issued at the time but they have never been found.
Police launched a major investigation to try to identify the men.
Officers carried out door-to-door inquiries in an effort to find out what had happened to Mr Ingram.
They also set up check points and stopped dozens of vehicles B979 Kinmundy to Blackburn road outside Mr Ingram’s home and on the nearby A947 Aberdeen to Oldmeldrum road
In the days following the incident DI Gauld appealed for anyone who had seen a red Vauxhall car which had been found crashed on the nearby disused railway line.
He also asked for information regarding a “significant number” of old kitchen and bathroom taps which had been stolen from Mr Ingram’s property days before he was found injured.
The taps, which are understood to be from the 1970s, went missing about 10 days before the incident.
Mr Ingram spent weeks in intensive care at Aberdeen Royal Infirmary and underwent brain surgery.
He was later transferred to Woodend where hopes for a recovery were high.
However his condition never improved and on June 2, 2011 he died in a care home in Inverurie.
More than 200 mourners packed Newmachar Parish Church for his funeral.
Following his brother’s injury, Mr Ingram’s brother Rob launched a neighbourhood watch safety campaign in the village.