He recalled the moment when the 15-year-old had hugged her sister Sharon at the bus stop in Livingston.

She had spent the weekend with Sharon and had enjoyed it so much that arrangements had been made for her to return the following weekend, he said.

It was snowing that day and there were doubts over whether the buses would be running, but those fears proved to be unfounded and Vicky boarded the bus to Bathgate shortly before 5pm.

The bus arrived in Bathgate around half-an-hour later and Vicky got off, intending to catch another bus to Falkirk that would take her home in time to watch an awards programme on TV.

The evidence of several witnesses suggested she was anxious about where to catch the bus, despite her sister repeatedly giving her directions.

She asked the bus driver, who also gave her directions, and a woman in a chip shop.

As she left the chip shop, she crossed the road, apparently when it was not safe to do so, as a driving instructor had given evidence of having to brake sharply to avoid colliding with her.

Mr Mulholland submitted there were two further reliable sightings.

One was from a man who was hiring a video and the other from the patron of a nearby pub who met a girl at the bus stop as he returned from buying chips.

“These are the last known, I would suggest reliable, sightings of Vicky Hamilton alive,” he told the jury.

He suggested that it was clear from the evidence she did not catch the bus to Falkirk.

So began a 17-year nightmare for her parents.

“The Crown case is that Peter Tobin is the person responsible for this nightmare,” he said.

Mr Mulholland said that to abduct, drug, sexually assault and murder a 15-year-old girl who was doing nothing more than trying to get home to her mother was a crime of almost unspeakable horror.

He suggested it was “a barbaric act — an atrocity” compounded by the attempt to conceal the crime by leaving Vicky’s purse at St Andrew Square in Edinburgh.

He suggested that Tobin had deposited the purse there “to deviously make it appear Vicky had run away from home”, with the obvious affect that would have on her family.

Mr Mulholland then turned to the finding of a body found interred in a concrete grave in the back garden of the house in Irvine Drive in Margate last year.

He suggested this was done to prevent Vicky’s family ever discovering what had happened to her, leading them to a life of “soul searching, wondering, what, if and why”.

Mr Mulholland said the case against Tobin was circumstantial, but that was not surprising as nobody was going to commit such an offence in front of witnesses.

A circumstantial case was built from a whole range of pieces of information which, when looked at as a whole, gave a clear picture.

He compared it to a rope constructed of individual strands which, though weak on their own, when woven together gave power and strength.

Mr Mulholland then suggested there were a number of facts known about Vicky. The first was that she wanted to get home to watch a programme of special interest to her.

Given the weather, her wish to get home and her continued insecurity about the journey back to Falkirk, she would not be inclined to dally in a town with which she was unfamiliar, he suggested.

It would not be odd behaviour for a 15-year-old girl on her own who was anxious about the journey to repeatedly seek reassurance about where to get the bus.

Secondly, Mr Mulholland suggested it was clear Vicky had not taken any intoxicants.

There was no record of her GP ever prescribing her anti-depressants or sedatives and no evidence that she was taking such drugs at the time of her disappearance.

Mr Mulholland said there was not a scrap of evidence Vicky had herself taken any tranquillisers willingly during her short life.

Her sister had confirmed that during the weekend they spent together Vicky did not take any drugs, he said.

None of the witnesses who saw Vicky in Bathgate spoke of her appearing to be under the influence of anything, and in fact she was described as “an ordinary teenager — a quiet and polite girl”, he said.

One witness had declared there was no way she was under the influence of anything that evening.

Pathologist Professor Busuttil had said that if she had taken anti-depressants it would have been obvious and she would have been unable to carry out the transaction in the chip shop without it being clear to the person serving her that she had taken something.

Thirdly, Mr Mulholland continued, he suggested it was clear Vicky was uninjured at the time of the last sightings.

Fourthly, he suggested from the evidence it was clear she was wearing a black bomber jacket, a sweatshirt, a polo shirt, jeans and shoes and was carrying two bags.

At this point, Mr Mulholland recalled two statements that had been put before the jury.

In the first, made shortly after Vicky disappeared, the witness spoke of meeting a girl aged around 17 in Bathgate. She was shown a photograph of Vicky but could not identify her.

However, in a statement 16 years later, the same witness said she was sure the girl was Vicky.

Mr Mulholland suggested this sighting could not be considered reliable and even if it was, “so what?” he asked.

Even if the girl had been Vicky it did not in any way exonerate Peter Tobin from this awful crime, he said.

Mr Mulholland said it would not have escaped the jury’s attention that the body found in two parts in Margate was naked from the waist down — wholly inconsistent with any notion of death by natural causes.

The clothing found on the upper parts matched Vicky’s, and one ring found was identified as belonging to her mother, while another was said to be similar to that given to her by her mother and seen in a photograph of Vicky taken on her last Christmas Day. DNA evidence from the body matched Vicky’s profile and finally dental records showed Vicky’s teeth matched that of the body.

Mr Mulholland said this conclusively proved the body was that of Vicky Hamilton.

The second clear fact about the body was that it had been cut in two, and he reminded the jury of a computer presentation they had been shown which detailed how the parts had been found.

The jury had also heard that the bisecting of the body was consistent with the use of a sharp, non-serrated knife.

Mr Mulholland then turned to the knife found in the loft of Tobin’s former home in Bathgate. It was, he pointed out, a sharp, non-serrated knife. He reminded the jury that when interviewed by police, Tobin had said the knife was his, or was probably his.

A piece of material found on the knife was, in the opinion of a forensic scientist, skin.

DNA analysis gave a one in more than one billion chance of the DNA coming from a woman unrelated to Vicky.

Mr Mulholland suggested this proved the skin on the knife was Vicky Hamilton’s.

He said the jury could be confident of the DNA evidence as a profile obtained from a bloodstain in the bathroom of the Bathgate house matched that of a former resident who had given evidence of cutting himself there while performing DIY.

The third thing the jury could find from the discovery of Vicky’s body was that it was wrapped in bin bags, like the layers of a “Russian doll”, one witness said.

From one of the inside bags wrapping the upper part of her body police found four of Peter Tobin’s fingerprints.

The solicitor general also observed that Vicky’s grave had been dug and her remains covered in concrete a long way from where she was last seen.

This, he suggested, was in an effort to allow the body to decompose and make it more difficult to establish the time and cause of death and conceal “this evil crime” from the authorities.

He said it was nonetheless clear following the discovery of the remains that Vicky had been drugged.

Not only was she drugged, she was drugged by a prescription drug Peter Tobin was familiar with because he had taken it for some time.

He had also been admitted to hospital suffering from an overdose of the sedative found in Vicky.

“There is no rational explanation to suggest she would take such a drug willingly.

“I would suggest the only rational explanation for the presence of such a drug, sedative, is that someone wanted to overcome her resistance. Someone wanted to render her defenceless and do her harm,” Mr Mulholland said.

Vicky’s remains also provided further evidence against Peter Tobin in relation to the swabs taken from an intimate area.

The Crown accepted that the external swab produced a partial profile which could have come from one in 114 of the population and the internal swab produced a profile which matched Peter Tobin and could have come from one in 34,000 other than and unrelated to Peter Tobin.

He told jurors forensic scientists had to look at such results in isolation but they could look at them in the context of all the other evidence and, Mr Mulholland said, they were thus, highly significant.

He submitted they could hold in these circumstances that the profile recovered from the swabs was Peter Tobin’s and the implication of this he described as “evil”.

Mr Mulholland said evidence of bruising to Vicky’s right hand and chest at or about the time of death and evidence from one of the pathologists that there was compression of the neck indicated the girl had died violently.

He asked jurors to accept that the evidence pointed to Vicky Hamilton having been drugged, sexually assaulted, subjected to violence, had her neck compressed and was murdered.

“The Crown case is that Peter Tobin wickedly intended to kill Vicky Hamilton and did so. I have searched hard in my lexicon to find words that can adequately describe what happened to this girl and the best I can do is evil,” Mr Mulholland said.

He said Peter Tobin was living at Robertson Avenue in Bathgate at the time Vicky disappeared, the house where police found a knife tucked away between a joist and the end wall in the loft.

He suggested this was “powerful” evidence on its own that Peter Tobin was responsible for her murder.

He described as damning the admission to police by Tobin that it was probably his knife.

Turning to the purse found in St Andrew Square, the solicitor general said it was put there and had the effect of police widening the search for Vicky, not unreasonably on the basis that she may have run away from home to London or Aberdeen.

It contained a ticket giving the date and time she took the bus from Livingston to Bathgate and its significance was not fully appreciated when it was handed in to lost property.

It was only after a letter was written to the owner that police realised its significance.

Swabs were taken from both sides of the purse and a DNA profile was obtained which provided a match to Peter Tobin’s son.

The solicitor general argued there was only a five-day window during which Peter Tobin’s son could have come into contact with the purse and the finding of his DNA on it suggested that Peter Tobin had either given it to the three-year-old to play with or allowed him access to the purse.

“How did he have the purse?” Answering his own question Mr Mulholland said, “He took it from Vicky.”

He continued, “How did he take it?” The solicitor general again answered his own question, “When he murdered Vicky Hamilton.”

During this time he said Peter Tobin was behaving in a way described by an electrician working at the house as, anxious, nervous and edgy.

The family with whom he was trying to arrange a house swap from Bathgate to Margate spoke of no-one being in on two occasions and, when they finally gained admission not being allowed into the house.

No-one was suggesting that this family had anything to do with Vicky Hamilton’s disappearance.

“The only other person with a connection between the two houses is Peter Tobin,” Mr Mulholland said.

The solicitor general said these were not the only links to Peter Tobin and the murder and disposal of Vicky Hamilton’s body.

He reminded jurors again of the presence of the fingerprints on the plastic bag and, in the context of the other evidence, he said they were, “incapable of having an innocent explanation”.

In conclusion he told jurors the file on Vicky Hamilton’s disappearance had never been closed by police.

“It was looked at again and again and again. I invite you to finally close this file and hold that this man, Peter Tobin, beyond reasonable doubt, killed Vicky Hamilton.”

The trial continues.

The charges:

Peter Tobin denies that on February 10, 1991, at a number of locations in Bathgate, he abducted, compelled or otherwise induced Vicky Hamilton, to accompany him to his home in Bathgate and there, or elsewhere in Scotland, assaulted her, drugged her, struggled with her, compressed or otherwise injured her neck, indecently assaulted her and murdered her.

He also denies that between February 10, 1991 and December 15 the same year, at his home in Bathgate, at St Andrew Square in Edinburgh, at an address in Margate and elsewhere in the UK he attempted to defeat the ends of justice.

That charge alleges he concealed Vicky's body; removed and disposed of items of clothing and footwear and other of her belongings; that, knowing a missing person enquiry was underway he deposited a purse belonging to Vicky under a portable building with intent to mislead police into believing she had run away from home, bisected her body with knives and similar instruments and bound and wrapped her body in coverings and bin bags; disposed of and concealed the knives; and that he concealed, transported and buried her body parts.

Tobin has lodged a special defence of alibi that between 5pm and midnight on February 10, when the crime was committed, he was in the Portsmouth area and then travelling from Southern England to Scotland and did not return to Edinburgh before 6.30am on February 11.