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Leanne Tiernan – compelling forensic evidence to hunt a killer
Forensic Science Service (FSS) expertise in a range of different fields helped provide compelling evidence for police hunting the killer of 16-year-old Leanne Tiernan.
Analysis of fibres and twine, Mitochondrial DNA testing and even dog DNA work were all carried out in the hope of finding a clue that would point to the schoolgirl's killer.
West Yorkshire Police launched a murder investigation following the discovery of Leanne's badly decomposed body in August 2001, nine months after she went missing following a shopping trip. Fingerprints, DNA and clothing identified the body as that of the missing Leeds teenager.
FSS experts were drafted onto the murder investigation team and co-ordinated the forensic input that eventually linked suspect John Taylor to the crime.
Leanne's body was discovered in a duvet cover and a number of green plastic refuse sacks. Her head was covered by a black plastic bag, which was held in place by a dog collar. A scarf and plastic cable tie had been tied around her neck and cable ties bound together her wrists.
FSS scientists concentrated their efforts on building up a forensic picture of the offender. This work, combined with police work relating to the supplier of the dog collar and cable ties, ultimately led police to Taylor.
The forensic evidence
Scarf - Scientists examined the knitted scarf found around Leanne's neck and discovered hairs caught in the knot. Conventional DNA tests on the hair roots failed, but using Mitochondrial DNA testing, a DNA profile was obtained from the minute amounts of DNA inside the hair shaft and it matched Taylor.
Twine – FSS experts examined the twine and discovered that it had an unusual composition. Examination of twine found at Taylor's home found it to exactly match that used to tie up the green bin bags. It was traced to a manufacturer in Devon who sold it for rabbit netting and only a small 'one-off' batch was ever made.
Carpet fibres - Red nylon carpet fibres were recovered from Leanne's jumper. When these were examined they were found to be very distinctive, due to the unusual way in which the fibre had been dyed. Examination of carpet fibres belonging to Taylor – which he had tried to burn – showed a match.
Dog hairs - animal hairs were found on Leanne's body and an FSS scientist took a sample of them to a Texan university that had developed DNA profiling for dogs, principally for pedigree research. A partial DNA profile of a dog was obtained. The results did not help the case as the dog Taylor owned at the time of Leanne's abduction had died. However, this was the first time a dog's DNA profile was obtained in a British case.
Taylor received two life sentences at Leeds Crown Court in July 2002 after admitting the kidnap and murder of Leanne.