AN expert biologist whose inattention on a motorway caused the death of a retired headmaster has been sentenced to carry out 200 hours of unpaid work.

St Andrews University research fellow Dr Nathan Bailey, a "world expert" whose work involves studying the sex life of wild crickets, failed to notice Ronald Highcock, 83, driving his Citroen Saxo slowly down the M9 near Bridge of Allan, Stirlingshire.

Bailey, 34, took evasive action too late - leading to his Renault Clio hitting the side of Mr Highcock's vehicle, and sending them both down an embankment, where Mr Highcock's car hit a tree.

Mr Highcock had been returning home from the Dunblane Hydro Hotel, where he and wife Elizabeth, 79, had been celebrating their wedding anniversary.

Letters of support for Bailey were written by senior staff at St Andrews University, including principal Dr Louise Richardson, and handed in to Stirling Sheriff Court, where he pleaded guilty to causing death by careless driving in the incident, which happened on April 28 last year.

Sheriff William Gilchrist sentenced Bailey, who is an American citizen but lives in Dundee, to 200 hours of unpaid work under a community payback order, disqualified him for a year, and ordered him to re-sit a full test if he wants to return to the roads.

He said it was "clear" the accident's cause was his failure to notice Mr Highcock's car was travelling on the motorway at "a slow rate".

He said: "This was clearly a tragic incident. Not only was it a tragedy for the deceased and his family it is also clear the accident has had a profound impact on you, particularly on your psychological wellbeing."