Lord Hardie told Ross: "This was a vicious, evil, unprovoked murder of a defenceless man. The attack was a pre-meditated assassination which involved the use of a firearm.
"It involved shooting him in the head at close range. It occurred in a public restaurant in front of members of the public, including children, who were traumatised by your actions.
"It was motivated by your extreme racist prejudice and after the murder you attempted to pervert the course of justice by destroying evidence."
He said: "Despite the fact that you are a first offender and were 15 on the date of the murder of Shamsuddin Mahmood, taking account of these aggravating factors, I consider that the appropriate punishment period that you should serve before being eligible for parole is 25 years. I sentence you to life imprisonment."
Lord Hardie also said that the evidence showed that Ross held racist views and sympathy for Nazi Germany.
The judge added that Ross had gone onto have a career in the army and have a family, but said he had "deprived" his victim of the opportunity to have a family or further his career.
Lord Hardie went on: "Your actions in murdering him were an act of cowardice and, despite what was said about your army career, it is clear from your actions after conviction, that you are still a coward."
Michael Ross is an evil person
Abul Shafuddin Shamsuddin Mahmood's brother
Defence QC Donald Findlay revealed that Ross continued to protest his innocence and said "everything will be done at his instruction in an attempt to clear his name".
Shamsuddin's brother Abul Shafuddin said: "At last the killer has been brought to justice - it's a big consolation for us. At one stage we lost all hope that his killer would be found.
"We cannot forgive him. He owes an apology to the family which he has not tendered. He is not a reformed person.
"There cannot be any other motive than racism. If somebody else was in my brother's place at that time - a black person - he might have killed him. Michael Ross is an evil person."
Orkney and Shetland MP Alistair Carmichael said: "This is something that has been hanging over Orkney as a community for many, many years.
"By and large the community will be relieved that at long last they can draw a line under this. Everybody must be satisfied that there has been some sort of resolution."
Northern Constabulary said in a statement: "Northern Constabulary welcomes the life sentence given to Michael Ross. This was a senseless and abhorrent act and the sentence reflects this.
"The sentencing today finally brings a conclusion to a long and difficult period for the family of Shamsuddin and the community in Orkney.
"Crimes such as this are extremely rare in Scotland and virtually unheard of in somewhere like Orkney. Levels of crime on the islands are extremely low and the detection rate for crime, which does exist is one of the highest in the UK."
However, Ross's father Eddie Ross said: "No one in our family believed he was responsible for what he was accused of."
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