The father of M9 crash victim John Yuill wants Britain's second most senior police officer called to give evidence at a Fatal Accident Inquiry (FAI).
Gordon Yuill says it's vital that Stephen House, Deputy Commissioner of the Met Police in London, is cited as a witness given his position as Chief Constable of Police Scotland at the time of the accident.
Yuill last week said the £100,000 fine handed to Police Scotland at the High Court in Edinburgh this month over the crash was pointless, as it will be covered by taxpayers, and said the family still have questions over why, in 2018, police scrapped the car involved without the family's permission.
John, 28, and Lamara Bell, 25, were returning from a trip when their Renault Clio left the motorway and plunged down an embankment near Bannockburn on July 5, 2015.
A call was made to police that day to report the crash but it wasn't followed up and officers only attended three days later when a further 999 call was made.
John died at the scene while Lamara passed away in hospital on July 12, a week after the crash.
Six years later, Police Scotland were fined after admitting call-handling failures materially contributed to Lamara's death.
It's claimed John would likely have died within minutes of the crash although a medical expert commissioned by his family's legal team believes he could have been saved with medical help.
House left his job in charge of Scotland's single police force five months after the crash, with a book about Nicola Sturgeon this year claiming the First Minister effectively dismissed him from his position.
Yuill, of Falkirk, said: "Our family has been through six years of hell because of the police's involvement and way authorities dealt with this.
"In usual circumstances, we would have been informed there had been a crash, we would have had a funeral and grieved. Instead, we have ended up with years of anguish.
"We intend to cite Stephen House as a witness and call him to give evidence as we want him to be accountable. The fact that he exited Police Scotland after the crash and then went down to get a senior job at the Met police is quite unbelievable.
"We expect the FAI to take place next year. However, with the car being scrapped, it could be difficult to prove what exactly happened.
"We are still awaiting answers on who decided to scrap the car and we are at a complete loss to understand how it was allowed to happen. It's destruction of evidence. Police said the families consented, but that is news to us.
"John had a right to dignity in death and didn't get it. Police Scotland have been fined £100,000 but one way or another, the public will pay this sum for the police's failure.
"The current Chief Constable Iain Livingstone has ended up stepping forward to take the rap. He apologised to us in court, which I appreciated, and has offered to meet with us and I will take him up on this."
Deputy Chief Constable Fiona Taylor said: "The Chief Constable has apologised unreservedly to the families of Lamara Bell and John Yuill on behalf of policing in Scotland and he would welcome the opportunity to meet with them to personally convey that apology and to discuss any matters of concern with them."
The Crown Office said: "The guilty plea was made after a tenacious investigation which overcame a series of challenges. Our attention is now on work in preparation of an FAI as we continue to strive to get the families the answers they deserve."
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