She revealed “you do feel these things very deeply” as she described the incident – in which police failed to respond to reports of a car going off the motorway for three days – as being a “dreadful failure”.
Despite that, however, she said she was “very proud” of the SNP’s record on policing, including the merger of eight regional forces to create the national body Police Scotland. Ms Sturgeon, who took over as First Minister from Alex Salmond in November 2014, is for the first time asking Scots to elect her into the role.
She said the deaths of Mr Yuill and Ms Bell were the lowest point in her career as First Minister.
“With any public service, not everything will go right all of the time,” she said.
“The dreadful failure in terms of the call that went unanswered at the police which resulted in a terrible tragedy for two families, that was obviously tragic beyond words for the families concerned.
“It’s still under investigation, so I can’t say too much more, but as First Minister you do feel these things very deeply.”
She added: “We’re very proud of the work that we have done to keep extra police on the streets, to create a single police force which allows us to cut out a lot of unnecessary duplication and bureaucracy in the police service, and therefore spend more money on frontline policing.”
The Police Investigations & Review Commissioner is also now looking into another incident after it emerged Police Scotland was contacted about the well-being of Andrew Bow, 36, a week before he was found dead in his flat.
With polls putting the SNP on course for a second majority at Holyrood after 5 May, she said her biggest challenge is “convincing people that success for the SNP is not guaranteed”.
She said: “It has to be delivered in the ballot box. That’s why I am spending so much time out and about, chapping the doors, convincing people that if you want to keep me as First Minister and want to have an SNP government, then it has to be both votes SNP.”
She added: “The only person not taking the outcome for granted is me and the SNP.
“We’ve got Labour and the Tories who, by their own admission, are battling it out for second place. That’s a strange place for any party to be in.”
Speaking at the Glad Cafe in Glasgow, a local business close to her constituency office in Pollokshaws, she hinted the SNP manifesto, which she will launch tomorrow, will include more detail on her plan to build a new “realistic and relevant” case for independence.
“Our job, and my job, in the years ahead is to try to persuade a majority of people that it is the right future for Scotland,” she said.
“We will set out, starting this summer, a programme of work to convince people – the people we didn’t convince in 2014 – of the case for independence.”
The recent downturn in the North Sea has left her enthusiasm for independence undimmed, she added.
“When you are faced with a fiscal position or an economic position that is less than you would want it to be, that is not an argument for the status quo – that’s an argument for change,” she said.
The First Minister will today address the Scottish Trades Union Congress in Dundee and pledge to stand “four square with union leaders to oppose the Tory government’s Trade Union Bill”.
The legislation has been branded “draconian” amid fears it will restrict workers’ rights to strike and picket, as well as clamping down on core union activities in the workplace. Ms Sturgeon will pledge to take action if re-elected to ensure trade unions can continue to operate effectively in Scotland.
“There is perhaps no starker reminder of the contempt with which the Tory government holds the trade union movement than this legislation,” the First Minister will say.
“The SNP will always value a strong, vibrant trade union movement which stands up for its workers. So we will continue to work with unions – to disrupt this bill, to do everything in our power to block it or to see the clauses rethought.
“And while we could simply argue for Scotland to be removed, we will continue to argue against the bill across the whole of the UK.
“It would be an outrage if the ability of the Scottish government to work constructively with trade unions was curtailed by the anti-union ideology of the Tories. If the SNP is returned as the government next month we will take every possible step to support trade unions.”