Fresh failings have been raised at a criticised police control room over the handling of reports of concern for a vulnerable man who was later found dead.
Report on M9 Crash Tragedy
The family of a woman who died after lying in a crashed car for three days say they're 'closer to knowing what happened'.
The Police Investigations and Review Commissioner watchdog has submitted a second report to the Lord Advocate on the circumstances surrounding the deaths of Lamara Ball and John Yuill in the M9 tragedy.
Lamara Bell died after lying in the crashed car for three days after it was first reported to police last July.
John Yuill had died earlier.
Mother of two Ms Bell was critically injured in the crash off the M9 near Stirling and died later in hospital.
Her partner Mr Yuill - who was 28 - died at the scene.
While the couple lay in the wreckage, police put out a missing-person appeal.
The new report examines why a phone call to police reporting a car off the road on July 5 was not followed up and the procedure followed to log the call.
Investigators also probed the 'robustness' of the missing-person inquiry and why this was not linked to the phone call.
It follows an interim report sent to the Lord Advocate - Scotland's top prosecutor - in November.
The Lord Advocate will now consider the findings in the second report before deciding what action to take, including whether to hold a fatal accident inquiry or start a criminal prosecution.
The Bell family said in a statement: ''The past eleven months have been one of heartache for us all, especially for Lamara's two children, Alysha and Kieran.
However, the sincere wishes and support from the local community and beyond has helped us greatly with the grieving process.
The pain of losing Lamara in such tragic circumstances will never go away, but with the completion of this supplementary report from the Police Investigations and Review Commissioner we are another step closer to knowing what happened to Lamara and John on that fateful day.''
The Yuill family added: ''We are pleased the supplementary report has been completed and that it will hopefully take us nearer to some insight or answers as to what happened with John and Lamara on July 5 last year.''
A Pirc spokesman said: ''The commissioner's investigators pursued numerous lines of enquiry, including why a telephone call made to Police Scotland on July 5 2015, which reported a car off the road, was not followed up.
The commissioner also examined the procedures used by Police Scotland to log the particular call made on July 5 2015.
The investigation also looked at the robustness of Police Scotland's missing-person inquiry and why this was not linked with the information received in the telephone call.
This has been an exhaustive investigation which has required many different facets of the incident to be fully explored.
The commissioner will undertake further enquiries as required.''
Assistant Chief Constable Kate Thomson said: ''Our thoughts remain with the family and friends of Mr Yuill and Ms Bell.
Anyone affected by this incident including their families, colleagues within the service and the communities we serve continue to be offered our support.
The Police Service of Scotland has worked with both Pirc and Her Majesty's Inspectorate of Constabulary Scotland (HMICS) to ensure that we fully understand the circumstances that led to the deaths of Lamara Bell and John Yuill, and any wider issues concerning our contact, command and control centres, and the service we provide to the public who call us.
We are committed to resolving any issues, which gave rise to this tragic incident and continue to implement the recommendations made by HMICS, under the scrutiny of the Scottish Police Authority.
We now await the decision of the Crown following their consideration of the Pirc report, and as such the service is not in a position to respond to specific issues or questions raised.''
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