So who is to blame for World's End trial fiasco…?

Since a ruling by Lord Clarke on Monday that Angus Sinclair, had no case to answer, criticism has been levelled at the prosecutor, Alan Mackay, for not leading all the available evidence.

However, in a statement to MSPs, the Lord Advocate, Elish Angiolini, QC, is expected to maintain the Crown's position that there had been enough evidence to allow the prosecution to continue. By implication, that would be saying Lord Clarke got it wrong.

It would not be the first time Lord Clarke had upset the Crown with decisions in a murder case. Earlier this year, following rulings by the judge, two men were acquitted of murdering a man thrown into a freezing canal.

A legal source revealed yesterday there was a train of thought that not every judge would have reached the same decision as Lord Clarke in the World's End case.

"The word is that perhaps eight out of ten judges would have let [the case] go to the jury. That doesn't necessarily mean he was wrong; it might just say more about the courage of Lord Clarke than others to make hard decisions which he must have known would cause a huge outcry. He does what he thinks is right, come hell or high water," said the source.

The Crown's view veers very much towards mistake rather than courage. Its first official response to Monday's collapse of the trial was to confirm that "low-probability" DNA evidence found on tights used to bind the victims had not been led by Mr Mackay.

But it insisted: "Laying aside this evidence, which was consistent with consensual contact with the victims, the Crown was of the view that there was sufficient evidence on which to base a prosecution. Further, given the basis upon which the judge approached the evidence which was led, we do not consider that this evidence, relating as it did to items of underwear worn by the deceased, would have persuaded the judge that there was a sufficiency."

Then, the Solicitor-General for Scotland, Frank Mulholland, QC, gave unstinting support to Mr Mackay, describing him as "a fantastic prosecutor" and fully backing his decision-making in the trial.

Any change of stance in today's statement to Holyrood by the Lord Advocate would be a major surprise.

As outlined by Mr Mackay in his submission to Lord Clarke, the Crown considers that the charges against Sinclair of raping and strangling 17-year-olds Helen Scott and Christine Eadie in October 1977 should have been allowed to go to the jury for it to deliver a verdict.

The allegation was that he had acted with his brother-in-law, Gordon Hamilton, now dead, in abducting the girls in Edinburgh and taking them to East Lothian where their bodies were found.

ALAN MACKAY, ADVOCATE-DEPUTE

Why did he choose not to lead more evidence?

IT IS a question that mystifies police and forensic scientists in the case, as they are convinced strong evidence against Angus Sinclair was not heard.

The most obvious answer is that Mr Mackay believed he had presented a sufficient case for the question of Sinclair's guilt or innocence to be put to the jury.

The Crown Office said as much in a statement issued a few hours after judge Lord Clarke ruled there was no case to answer.

"The Crown was of the view that there was sufficient evidence on which to base a prosecution," it said.

Some onlookers have suggested Mr Mackay was wary of confusing the jury with too much DNA evidence.

Others have speculated that he was feeling off-colour and some have argued that a more senior prosecutor, such as the Solicitor General, Frank Mulholland, should have been in charge of such a complex case.

Another possibility is that a hitch during the testimony of forensic scientist Dr Jonathan Whitaker prevented some forensic evidence from being laid before the jury.

ELISH ANGIOLINI, LORD ADVOCATE

How much did she know?

THE Lord Advocate, as head of the Crown Office and Procurator Fiscal Service and Scotland's most senior law officer, takes ultimate responsibility for the prosecution of crime.

But it is the job of the advocate-depute, who in the World's End case was Alan Mackay, to prepare the trial and lead evidence in court.

However, others are on hand to give advice. As members of Crown counsel, Ms Angiolini and Frank Mulholland, the Solicitor General, would be among those available to give that advice. It would seem most likely that Mr Mulholland, who is effectively Ms Angiolini's number two, was consulted, having supervised the case against Angus Sinclair after being appointed area procurator-fiscal for Lothian and Borders in January last year.

A source said: "It is for advocate-deputes to take decisions on how to lead evidence and structure to a case, but they have sources of advice available to them."

Ms Angiolini will today make a statement to MSPs at Holyrood about the Crown's handling of the World's End murder trial.

LORD CLARKE, TRIAL JUDGE

Was he right to throw out the case?

THE World's End trial collapsed when the judge decided the prosecution had failed to present enough evidence to allow the charges against Angus Sinclair to be put before the jury.

No-one predicted a case that took 30 years to prepare would end in a "no case to answer" ruling.

In a statement to MSPs, Lord Advocate Elish Angiolini is today expected to state her belief that there had been enough evidence to allow the prosecution to continue - in effect saying Lord Clarke got it wrong.

Lord Clarke is grounded almost exclusively in civil, rather than criminal law, leading some to question his suitability to preside over such a complicated case.

Lord Matthew Clarke, who grew up in Hamilton and attended Glasgow University, became a solicitor in 1972.

He appeared for Celtic FC when the club fought off a claim for damages by its former manager, Lou Macari.

He joined the Supreme Court's bench in Scotland in 2000.

EDGAR PRAIS, DEFENCE QC

His 'no case to answer' motion ended the trial

ONE of the most colourful characters of the Scottish legal establishment, Edgar Prais, QC, led Angus Sinclair's defence during the World's End trial.

Mr Prais is an experienced figure who has been involved in many high-profile cases, both as a prosecutor and defence lawyer.

Two years ago, the 63-year-old travelled to the remote South Atlantic island of St Helena to represent a man accused of murder. During his time on the British-dependent territory, Mr Prais stayed at the house where Napoleon spent his last years in exile.

In June, he secured an acquittal for his client, Mansoor Khan, who had been accused along with Athif Sarwar of laundering 850,000 in a VAT fraud. Sarwar, the son of the Glasgow MP, was convicted.

In 2005, Mr Prais successfully defended police constable Dean Stewart in a case where the prosecutor was Alan Mackay.

The Strathclyde constable was cleared of ten of 13 sexual offences, including rape and abduction, at the High Court in Glasgow.

THE EVIDENCE THAT WAS LED

THE prosecution's case against Angus Sinclair, below, was based on his three links to the accused.

Scientists established that semen on the lining of Helen Scott's coat came from Sinclair.

The chance of it being from someone else was one in a billion.

More than 50 fibres were found on Helen Scott's coat, and these matched the fabric used on the upholstery of Sinclair's Toyota Hiace caravanette.

It was a new coat, and the findings indicated she had been in the van that night, although at what stage and where, it was not known.

Advocate Depute Alan Mackay attempted to show that Sinclair had been with the women when they were murdered.

The prosecution said it was important that the jury should consider that neither of the girls had worn her pants after sex. This was known because of the lack of semen stains on the pants. Christine's pants had been used as a gag while Helen's pants were found lying near her face.

EVIDENCE THAT WAS NOT LED

GENETIC material found inside the knots in ligatures used to strangle Christine Eadie, below, and Helen Scott, strongly linked both Angus Sinclair and Gordon Hamilton to the murders.

Forensic scientists were able to extract DNA material from inside the knots on the tights used to bind and strangle the girls. Two distinct profiles were discovered: one a complete match with Hamilton, the other a partial match for Sinclair.

The Crown Office say this evidence was consistent with the men having consensual sex with the girls. But police insist it pointed to both being involved in the murders. Jonathan Whitaker, the forensic scientist who gave evidence, earlier told detectives the DNA indicated the tights had been "gripped hard", suggesting the men did not merely brush against them during the sex.

The jury heard nothing about two different types of knots used to tie the ligatures, indicating that two people were involved.

No evidence was led about the girls' characters. Helen was a virgin and although Christine had had sex before she was not promiscuous. The pair were not likely to have agreed to have sex with two strangers.

THE RULES ON SUFFICIENCY

THE prosecution must present sufficient evidence linking an accused with a crime for a jury to be allowed to reach a verdict.

The minimum standard is that two independent corroborating pieces of evidence must be presented which point to an accused's guilt.

In deciding whether there is a case to answer, the judge must take the Crown's evidence in its best possible light.

This means that the judge must allow a case to be considered by the jury if the evidence relied on by the prosecution can possibly be interpreted as indicating the accused's guilt.

Whether that evidence is of sufficient quality to prove guilt beyond reasonable doubt is a question that only a jury - in the most serious cases like murder and rape - should decide.

The prosecution will bring a case to court only if it is satisfied that it has achieved the minimum required standard of evidence.

Elish Angiolini, the Lord Advocate, is today expected to state that this was the case when Angus Sinclair was brought to trial for the World's End murders.

WHY EVIDENCE WAS NOT ENOUGH

DURING a legal debate at the end of the prosecution case, Edgar Prais argued that there was nothing to show that any sexual encounter between Sinclair and the girls had not been consensual.

While it was beyond question that Helen and Christine had been murdered, he said there was no evidence to link Sinclair to their deaths.

As for robbery, Mr Prais said all the Crown had shown was that some clothing was missing.

He said there was nothing to show that Sinclair was in the World's End, or elsewhere in Edinburgh.

If there was a rape, he added, there was no way for the Crown to say whether Sinclair or Hamilton had committed it because there was no evidence of the sequence of events.

The QC said there was evidence that the two girls had been bound, gagged and beaten but said there was no evidence it was "a two-man job". This raised a question over which man - Sinclair or Hamilton - was then responsible, he said.

Dismissing the case, Lord Clarke said that although Sinclair could be shown to have had sex with at least one girl, the evidence was not strong enough to link him to the murders.

WHAT WENT WRONG?

THE prospect of securing a conviction in the World's End trial appeared to diminish rapidly as the prosecution case neared its end. The seeds of the Crown's difficulties seem to have been sown when Jonathan Whitaker, a recognised authority on DNA profiling, was in the witness box.

His evidence was interrupted by an objection from Edgar Prais. When the evidence resumed, copies of a report prepared by Mr Whitaker were removed from the jury.

The contents of the report are unclear, but it may have related to evidence that linked Sinclair to the ligatures used to bind and strangle Helen Scott, below, and Christine Eadie.

In dismissing the case, Lord Clarke made specific reference to the trial having heard no forensic evidence of such a link.

The defence had earlier admitted that if such evidence was presented, it would have to withdraw its application that Sinclair had no case to answer.

In his address to the judge on Friday, which could not be reported until the end of the trial, Mr Prais said: "If there had been evidence of Sinclair having tied up the girls, for example DNA evidence on ligatures, something of that nature, I do not think I would be standing here."

WHY WAS SINCLAIR NOT TRIED FOR OTHER MURDERS?

SOME police officers had wanted the Crown to charge Angus Sinclair with four other murders in the west of Scotland. He has been linked to the killings of Anna Kenny, Hilda McAuley and Agnes Cooney, below, who died similar deaths to Miss Scott and Miss Eadie in 1977. Police also believed he could be held responsible for killing Frances Barker earlier that year.

No DNA evidence remains to pin these four murders on Sinclair, but detectives believe he could have been shown to be responsible for the deaths due to the similarities with the World's End case. However, the Crown opted to try and secure a conviction for the deaths of Miss Scott and Miss Eadie alone.

The evidence was far stronger in the World's End case than in the other murders, while charging Sinclair with six killings rather than two would have made for an even more fraught case. But the decision to press ahead with the World's End murders alone was one that most police officers ultimately understood.