A father who stabbed his son to death and tried to murder a young girl has lost a bid to have his 16-year jail sentence reduced.

On Friday, Karl Morris, also known as Andrew, watched by video link from HMP Perth as judges at the Court of Criminal Appeal in Edinburgh refused his challenge against the sentence imposed on him.

Lord Turnbull, who heard the appeal with Lord Drummond Young, said: "We are not persuaded that the sentence selected can be described as excessive."

The appeal judges said they had concluded that they did not consider Lord Mulholland, who jailed Morris, could be criticised in any way for the approach he took in sentencing "in this most serious of crimes".

Morris, 39, was originally charged with murdering his ten-year-old son Kane in a knife attack at a flat in Coupar Angus, in Perth and Kinross, on November 11 last year.

But the Crown accepted his guilty plea to the lesser offence of culpable homicide on the basis of diminished responsibility.

He admitted killing the schoolboy by repeatedly striking him on the body with a knife at the property in Union Street.

He also admitted assaulting the eight-year-old girl during the same incident to her severe injury and the danger of her life by repeatedly striking her with a knife in a murder bid.

Morris stabbed Kane six times – once in the chest and five times in the back.

A stab wound he inflicted to the girl's stomach transfixed her liver and she would have died had it not been for immediate medical attention.

Morris also stabbed himself before jumping from a third floor window.

After medical treatment he was sent to the State Hospital at Carstairs for psychiatric assessment.

Reports noted that he had a history of coping poorly with stress. His stepfather had died earlier in the year in an industrial accident.

His workload had increased which had coincided with family and financial pressures.

But the court heard that those who saw him shortly before the attacks on the children occurred had no concerns about his behaviour.

In the appeal it was argued that Lord Mulholland gave insufficient weight to the mitigating factor of Morris' mental state in assessing the sentence to be imposed.

Lord Mulholland took as his starting point a 20-year sentence before reducing it to 16 years following the guilty pleas.

Ximena Vengoechea, counsel for Morris, said he was a hard working man and had been a doting father.

She argued that the starting point chosen by Lord Mulholland was "excessive" and a lower sentence reflecting the circumstances of the case should be selected.