The family of three victims of the Glasgow bin lorry crash have launched a bid for a private prosecution of driver Harry Clarke.
Six people died when the vehicle went out of control in Queen Street in December 2014.
A Fatal Accident Inquiry (FAI) held last year heard Mr Clarke lost consciousness at the wheel and that he had a history of health issues - including a previous blackout in 2010 when at the wheel of a stationary bus - but had not disclosed his medical background to his employers or the DVLA.
The Crown Office has consistently said that there is insufficient evidence in law to raise criminal proceedings against Mr Clarke but the families of the victims disagree.
It was revealed during the FAI that some families intended to launch a private prosecution if the Crown Office would not take action.
Lawyers for the family of Jack and Lorraine Sweeney and their granddaughter Erin McQuade have confirmed a Bill for Criminal Letters has been sent to the Crown Office that they hope will lead to a private prosecution.
The rare Bill for Criminal Letters seeks the agreement of Lord Advocate Frank Mulholland QC to pursue the case but lawyers said it can still continue and be ruled on by High Court judges without his approval.
A statement from the Sweeney and McQuade family lawyer said: "Paul Kavanagh, Gildeas solicitors, intimates on behalf of the relatives of Jack and Lorraine Sweeney and Erin McQuade that a Bill for Criminal Letters was delivered to the Lord Advocate today.
"We have sought the concurrence of the Lord Advocate and look forward to receiving a response within seven days.
"This is the initial process that the family hope ultimately will lead to the prosecution of Henry (Harry) Clarke in the criminal courts."
A spokesman for the Crown Office said: "The Lord Advocate has received a Bill of Criminal Letters and will give it due consideration.
"The Crown position on this will be made clear to the families and the court when appropriate."
Last month, Mr Mulholland insisted it would have been ''wrong'' to prosecute Mr Clarke.
He said he knew the decision not to charge the 58-year-old was ''not a popular one'', adding he was aware of the feelings of the victims' families on the matter.
The sheriff who oversaw the FAI ruled that the accident might have been prevented if the driver had ''told the truth'' about his history of blackouts.
Sheriff John Beckett QC found Mr Clarke ''repeatedly lied in order to gain and retain jobs and licences'', and ''deliberately concealed relevant information from the DVLA''.
Stephenie Tait, Jacqueline Morton and Gillian Ewing also died in the tragedy which was marked with a memorial service in Glasgow last month.