Ronnie Coulter's conviction after a retrial is the culmination of a legal saga that has spanned the best part of two decades.

The failure to secure any convictions in the months after the killing of Surjit Singh Chhokar sparked two independent inquiry reports into the handling of the 1998 case.

Their subsequent publication led to an admission by the top law officer at the time that the Chhokar family had been failed by the police and prosecution services.

Read more: Man found guilty of murdering waiter Surjit Singh Chhokar

Securing justice for the victim's relatives seemed an impossibility at that stage and was only made a reality thanks to a significant change in Scots law five years ago.

Coulter's retrial for Mr Chhokar's murder is only the second "double jeopardy" case held since the legislation which prevented a person being tried twice for the same crime was reformed.

Mr Chhokar, 32, was stabbed to death in Overtown, North Lanarkshire, as he made his way home from work on November 4 1998.

Three men - Coulter, his cousin Andrew Coulter and David Montgomery - were arrested and their cases were heard in two separate trials, in 1999 and 2000. All were acquitted of murder after blaming each other for the killing.

The case sparked controversy after the failure of authorities to secure a conviction.

Two official inquiries were ordered, looking at the treatment of the family and decision-making processes.

Read more: Man found guilty of murdering waiter Surjit Singh Chhokar

One report raised the issue of "institutional racism" and, following their publication in 2001, the Lord Advocate at the time, Colin Boyd QC, said the Chhokar family had been failed by the police and prosecuting authorities.

The prospect of securing a conviction was lost at that stage, with the murdered man's late father Darshan Singh Chhokar at one stage declaring he had ''nothing left'' after years of fighting for justice.

It was only with reform of the 800-year-old double jeopardy law in 2011 that the prospect of a conviction became a possibility.

A suspect could now face retrial for a very serious crime if "compelling new evidence" emerged, if the original trial was tainted or where a suspect admitted the offence.

The then justice secretary Kenny MacAskill said the move made Scots law "fit for the 21st century" and insisted the overhaul would only affect the "worst and most sickening" cases.

The first trial following the change was over the notorious 1977 World's End killings.

Read more: Man found guilty of murdering waiter Surjit Singh Chhokar

Serial killer Angus Sinclair's first High Court trial for raping and murdering teenagers Christine Eadie and Helen Scott collapsed due to insufficient evidence in 2007.

The 71-year-old was convicted in November 2014, at the second time of asking, and jailed for at least 37 years - the longest minimum sentence imposed by a Scottish court.

In the Chhokar case, police were instructed by the Crown Office at the start of 2012 to carry out a new investigation.

The Crown applied in May 2014 to set aside the acquittals of the three original accused.

Appeal judges ultimately granted them permission to retry Ronnie Coulter but ruled that Andrew Coulter and Mr Montgomery should not stand trial again.

Now, finally, Ronnie Coulter faces life behind bars for one of Scotland's most notorious killings.