A LAWYER representing the son of Lamara Bell, left in a crashed car for three days because police failed to respond to a call-out, has told of the family's distress over the length of time the investigation process is taking.

It comes days before the July 5 anniversary of the tragedy in which Ms Bell, 25, and her partner John Yuill, 28, from the Falkirk area were involved in the crash near Stirling after a camping trip.

READ MORE: Report takes us a step closer to knowing what happened

Mr Yuill died in the crash and although Ms Bell, who had a five-year-old son Kieran Burt, was conscious when officers did arrive at the scene but she died four days later in hospital.

Last month the Police Investigations and Reviews Commissioner passed a second report to the Lord Advocate who is still deliberating whether the next step will be a fatal accident inquiry or potentially criminal charges.

The Herald:

Aamer Anwar, instructed to act as the solicitor in the interests of Keiran Burt, said the length of time of the process is taking its toll on family members.

He said: "Clearly the length of time taken by the inquiry is causing distress to loved ones.

"It is a complex inquiry that Pirc have had to carry out, but it is hoped that the (Lord Advocate's) investigation won't be as complicated."

The Pirc supplementary report followed an interim report in November.

READ MORE: Family of M9 crash victim Lamara Bell hit out at First Minister over tragedy comments

Kieran's father Lee Burt and the boy's grandfather James McMillan said earlier: "At the heart of this tragedy is Kieran who never stops speaking about his mum.

“Some mornings he will wake up a happy boy because he dreamt of Lamara, but it is heart-breaking when a little boy tells you he misses his mum and the sound of laughter changes to silence."

Already the HM Inspectorate of Constabulary in Scotland made a raft of recommendations, after its largest investigation to date, calling for an urgent review of procedures.

Mr Burt, Ms Bell's former partner, accused Police Scotland of a "reckless disregard for public safety" after weaknesses in the force's call handling were found.

The Scottish Police Federation said it had issued warnings about staff cuts as the single force moves towards saving £1 billion while Police Scotland said it would respond to all 30 recommendations made by HMICS.

READ MORE: M9 crash deaths my lowest point as First Minister - Nicola Sturgeon

In statement in response to the submission of the Pirc report last month the Bell family said they are "another step closer to knowing what happened to Lamara and John on that fateful day".

A statement on behalf of the Yuill family said at the time they 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 spokesman for the Crown Office and Procurator Fiscal Service said: "The Police Investigations and Review Commissioner has submitted a supplementary report to the COPFS in connection with an incident on the M9 in July 2015.

“This report is being carefully considered by prosecutors and it would be inappropriate to comment further.

"The families of those involved will continue to be kept updated in relation to any significant developments.”