CONTAMINATION OF evidence in “cold” cases is an inevitable consequence of the extent of knowledge at the time evidence was gathered, a DNA expert told the High Court in Edinburgh yesterday.

Dr Jonathan Whitaker, on his fourth day in the witness box, was cross-examined by defence counsel Mark Stewart QC on his approach to evidence relating to the death of Elizabeth McCabe, who was found in Templeton Woods in 1980, two weeks after she was last seen in Dundee.

He pointed out the analysis of DNA was not offered as a forensic tool before 1988 and said issues of contamination are present and considered in any historic case, adding, “They are there, in your face.”

Mr Stewart referred to DNA tests of Vincent Simpson, who denies Miss McCabe’s murder, and evidence in the case, including some of Miss McCabe’s clothes and possessions.

He referred to the results of the tests being laid out on tables of boxes, with a number in each box showing parts of a DNA profile. In the boxes with no number the results had been negative.

Mr Stewart said in one partial profile from Miss McCabe’s jacket, one of the boxes at the bottom of the table had a number 18 and the DNA profile of Mr Simpson had the same number in the corresponding box in his profile.

He put it to the witness it had been technically possible for the 18 in the jacket sample to have appeared in the top row of the table instead, arguing, because of this, the graphic had been designed to make it look more incriminating to Mr Simpson.

The witness, who was not involved in the design of the graphic, replied, “I don’t know what the intentions were.”

He was also taken through a series of DNA samples from Miss McCabe’s possessions.

Dr Whitaker agreed that of 20 possible matches in the DNA tables the various items had only between six and 10 matches with Mr Simpson’s profile.

The court also heard when DNA samples are taken from physical evidence with no visible stain, an area is selected and a damp swab run over it.

Mr Stewart said, “You could pick up any number of DNA samples from any number of persons.”

Dr Whitaker said, “That’s what we are trying to do.”

Agreeing it was he who decided how many times a sample would be tested, the doctor was asked if he was aware some material he examined was found in a sweeping and taping exercise in November 2004, and said he was.

However, he was not aware of what counsel said was, “the self-same sheet subjected to the self-same examination in March 2003, when nothing was found.”

He agreed they found a profile from a hair, later identified as from a detective, and DNA profiles from two other people also connected to Tayside Police during the 2004 exercise.

Dr Whitaker said he was not aware of a profile similar to a pathologist in Dundee, Dr Donald Rushton, also being found.

Mr Stewart referred to another hair, from which a partial profile was obtained. When it was run through a staff database it was discovered there were eight possible police officers it could be from.

Dr Whitaker said he was not aware of this.

Mr Stewart suggested “vast swathes” of unidentified DNA were recovered and the “soup of DNA” could include anybody.

Dr Whitaker said when there is a “complex profile,” it is not regarded of any worth.

Referring to a partial profile from Elizabeth McCabe’s jacket, Mr Stewart asked if the process started with the assumption her own DNA would in swabbings taken. Dr Whitaker agreed.

Mr Stewart suggested the mixed profile was simplified by removing all Elizabeth McCabe DNA and seeing what was left.

He suggested the next step was to extract elements fitting the accused’s profile and Dr Whitaker agreed.

The doctor also agreed even after the McCabe and Simpson elements were removed there was still a rogue element.

He agreed analysis of a slide of biological material from a bank bag, which matched Mr Simpson, had “certainly focused the police inquiry.”

Counsel suggested this and other factors were skewed in favour of implicating him.

Mr Stewart cited factors such as a comparison with Forensic Science Services’ database and the national database for England and Wales, rather than the Scottish database, as examples.

If compared against the Scottish database the likelihood of it coming from someone other than Vincent Simpson was one in a thousand, compared to the one in 1300 the witness told the court earlier.

In one of the partial profiles obtained, running it against the Scottish database produced 8489 possible matches and when it was run against the Tayside Police staff elimination data base, it produced 27 possible matches. The UK database declined to run it because they would obtain too many “hits.”

Dr Whitaker said the England and Wales database was appropriate because the accused is English. It represented 50m people, compared to the Scots database of five million.

He said 15 areas of the jacket were tested but results of only three were reported. For the jumper, several areas were swabbed and one result reported.

Mr Stewart asked if he stopped the test because of an instruction or if it was his decision, and was told it was a Tayside Police instruction.

Mr Stewart put it to him he did not know whose DNA might have been found if further tests had been carried out, and Dr Whitaker agreed it was the case.

He was also asked about tests on swabs taken from jeans. Samples from near the fly had partial DNA profiles which did not match each other.

They also did not match a sample from a bank bag which had features in common with Vincent Simpson’s profile.

Dr Whitaker agreed another jeans sample was traced to DNA from a Charles Lamont.

Other samples showed complex mixed DNA results from at least three people and it was not possible to separate them into component parts.

Re-examined by advocate depute Alex Prentice QC, Dr Whitaker said he stood by his findings and saw no reason to modify his statement.

Retired police officer Frank Brown (64), told the court he was detailed to take a statement from an employee of the Chevalier Casino in the Seagate on March 4, 1980.

He took possession of a note from Charles Mathieson, who has since died.

It asked him to contact the accused and gave his Newtyle phone number.

When he called, Mr Mathieson told the officers, the accused was out but Vincent Simpson phoned that night.

“He said police might be coming to see me and wanted me to confirm he was in the Casino,” suggesting the times midnight and 1am on February 11, 1980.

“I told him I did not know him and could not remember,” the statement continued.

The trial continues.