The body of Arnold Mouat (64) was found there a month after concerns were raised over his whereabouts.
Kate Frame, the Police Investigations & Review Commissioner (PIRC) said the inadequate search by the specialised police team added to the distress and uncertainty of Mr Mouat’s family.
He had been reported missing on July 7 last year, having last been seen shortly before midnight the previous day.
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In a report published today, the Commissioner said Police Scotland recorded officers took 40 minutes to search Mr Mouat’s home, gardens, vehicle and garage with the search of the garage and gardens completed within five minutes.
The search continued until August 7 when a relative discovered his body in the roof space of the garage.
Ms Frame said: “Clearly, if the police had carried out a thorough search of the garage area, then it is highly likely that they would have discovered Mr Mouat’s body, something acknowledged by Police Scotland’s own internal review.
“In light of this case, I have made several recommendations which I have shared with the Deputy Chief Constable to enable him to put measures in place and take corrective action to prevent such failings happening again.”
The PIRC investigation also found items of evidence which were seized during the search were not recorded or documented as required by the force’s own procedures.
The PIRC report said Police Scotland’s internal review concluded that, “crucially the search in the area of the garage cannot have been deemed to have been thorough and systematic, even if the remit had originally to have been only to look for the mission person, all indications are that he was within the garage from day one”.
Chief Superintendent Matt Richards said: “I apologise on behalf of Police Scotland and once again offer my sincere condolences to the family and friends of Arnold Mouat. I fully accept the findings from the review by the Police Investigations & Review Commissioner and Police Scotland will continue to work with them to ensure all the lessons identified are addressed and built into our search procedures and protocols, much of which is already in place.”