First Minister Nicola Sturgeon has told how her "heart breaks" for the family of murdered schoolgirl Paige Doherty in response to Tory pleas for Scotland to have whole-life prison terms.

Paige's killer, John Leathem, was given a mandatory life sentence and ordered to spend at least 27 years behind bars before he could apply for parole for the frenzied knife attack on the 15-year-old.

Leathem admitted killing the teenager after she came into his deli-shop in Whitecrook last March.

Last week judges at the Appeal Court in Edinburgh quashed the original punishment and imposed a 23-year minimum sentence.

The decision prompted Scottish Conservative leader Ruth Davidson to call for whole-life sentences to be introduced north of the border.

She challenged Ms Sturgeon on the issue at First Minister's Questions at Holyrood, saying if the Scottish Government did not act her party would bring forward a member's bill to try to make the change.

Ms Davidson said: "As it stands, our judges do not have the tool of a whole-life tariff at their disposal and we say that they should.

"We can sit in this Parliament and we can wring our hands and we can express outrage every time something like this happens, or we can do something about it.

"And I want to do something about it."

Ms Sturgeon said her government would "reflect further" on the issue "about what further changes we might think appropriate".

But Ms Davidson pledged: "If the Scottish Government won't act, then I can say the Scottish Conservatives will do so by pushing ahead with a member's bill making the case for the introduction of whole-life sentencing in Scotland.

"We need to stand up for families who see sentences for murder cut less than a year after they have been handed down and we should change the law so that families like Paige Doherty's feel that the law is tipping back in their favour and that the worst criminals are kept off our streets forever.

"We have waited too long. Isn't it time we all acted?"

Ms Sturgeon said her "heart breaks" for the family of Paige. She met with mum Pamela Munro last year and said there were "no words to express the pain and grieve she and they have gone through".

She continued: "I have no difficulty in understanding the sentiments that were expressed by the JusticeForPaige campaign. If I had been a relative of Paige Doherty I would have felt exactly the same.

"The only thing I would say, and this is the more difficult thing for me to say - this was a decision of an independent judge in a court of law. We have an independent judiciary in this country.

"As well as being First Minister, I'm a human being. And there are many occasions where I look at decisions of courts and wish the different decisions had been reached. And this may well be one such case.

"But I respect the indepndence of the judiciary. I don't think anybody in this chamber would expect me to interfere with those decisions. But what I can do today is say, absolutely, that I understand and I sympathise with the pain and grief that this family has experienced."

The Scottish Sentencing Council is currently looking at guidelines for sentencing and Ms Davidson said appeals should be part of their work. The First Minister said she would be happy for it to consider the issue, and that the government and parliament would consider any changes if needed.

Ms Sturgeon continued: "While we have an independent judiciary and courts must be allowed to take their decisions, the framework and context of those decisions is very often set by parliament.

"But no matter what framework and context parliament sets on any of these issues, we will still have instances where decisions by courts are decisions many people feel are the wrong decisions. That's in the very nature of an independent judiciary."

Ms Davidson said "too many families" did not feel they were "getting the justice they deserve" and that the "dice were loaded" against the victims.

The First Minister said: "I don't think it is fair to go from one case where we're all agreed in our characterisation of it, to say families are routinely let down by the justice system.

"None of that takes away from the pain and anguish felt by a family that has experienced what Paige Doherty's family has experienced.

"I think it's important, calmly and rationally for government and for parliament to consider periodically whether the rules are the right rules or whether they require to be changed. I can give an assurance we will always seek to do that.

"No matter what sentencing rules we have in place, no matter what frameworks we have in place, because we have, rightly and properly, an independent judicial system in this country, there will always be decisions taken by judges that some of us think are the wrong decisions.

"I don't want to comment too much more on the individual case of Paige Doherty - I think we're all agreed on the tragic nature of that case. But if the system that Ruth Davidson is advocating had been in place, there is no guarantee that that is the sentence a particular judge would have opted for."

The European Court of Human Rights has ruled in recent years that in the UK and elsewhere there must at least be an opportunity to be considered for parole, even if it isn't granted. The UK government has said it plans to withdraw from the court.