DNA Crime Investigations by Stephen Wade

Author:Stephen Wade [Wade, Stephen]
Language: eng
Format: epub
ISBN: 9781844688142
Publisher: Wharncliffe
Published: 2012-03-28T16:00:00+00:00

Then, as to the DNA work, what happened was that the DNA evidence against Castree was from a ‘tapelift’ from Lesley’s knickers. Because this item is simply a piece of sticky tape, the obvious fragility of that led the lawyers for Castree to ask about its reliability and how it could have been contaminated. Forensic scientist Roger Robson worked on the case.

It has to be recalled that in 1975, DNA played no part in forensic work for police investigation. But items of clothing were kept, and Robson, together with Clare Stangoe and Ted Kinner, knew how to work with the vestigial remains of the case records. A meeting was held with the lawyers and a strategy put together. In a newsletter called Benchmark, in 2008, the next step was described: ‘Roger and Clare had to try to understand how Castree’s DNA could have been transferred to a sticky strip that had DNA from the clothing (destroyed in the 1980s) – was this due to contact between Lesley and Castree, or to contamination in the forensic laboratory?’ This might seem like splitting hairs in terms of the defence counsel for Castree – desperation in effect. But the fact is that in court, the slightest doubt about evidence can blow a case out like a house of cards coming down.

The scientists had to go to Wetherby, where the Forensic Science Service labs are, and look very closely at the location and the general procedures for materials and fabrics in cases like these. Their findings were vital to the success of the prosecution of Castree. First, they confirmed that just the one lab was used with the materials from the case; no precautions were taken to avoid DNA contamination (because DNA was not used!) and that the tapes had been opened and closed, and so could have been contaminated. As Castree had been busy attacking and having some kind of sexual contact with various females in the intervening years, the question arose: could his DNA from other procedures in the lab have contaminated the sticky strip from Lesley’s clothing?

The report on this given to the court was obviously very important. Opinions had to be given, and in terms that the jury could comprehend. It was a procedure to admit that such contamination was theoretically possible, but the high improbability of such a thing has to be stated. In the end it was the recurrence ratio of a billion to one that led to the conviction. It was a disturbing and emotional trial; the jury were given black and white photos of the murder scene, and also of the Turf Hill estate where both Lesley and Castree had lived in 1975. The revolting nature of the attack was described yet again, as if history had been re-enacted, even down to the details of the dozen stabbings on the girl’s body and the note that the wounds were made with such force that, as Mr Goose for the prosecution said, ‘The knife hilt or the killer’s hand, had caused bruising.

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