Stephen Jakobi, the Smith family's London solicitor, told the Independent last night that the Government Chemist had provided 'absolute proof' that the teenagers had been framed, and he urged the Foreign Office to take every step to ensure their early release from prison in Bangkok.
'We have had the case of the Taylor sisters only last week, where the suppression or distortion of police evidence caused instant release, on appeal,' Mr Jakobi said. 'I hope the Thai authorities would behave as any other in the light of this new evidence. Karyn Smith and Patricia Cahill have been wrongfully convicted.'
The first hard evidence of a miscarriage of justice has been given in a letter sent by Terry Gough, head of the Government Chemist's Forensic and Customs Division, to the Foreign Office Consular Department last month.
Dr Gough explained that although he was unable to comment on the evidence given in the trial - having seen neither the judgment nor the exhibits - the laboratory had built up an expertise in 'the physical and chemical characteristics of heroin'.
He suggested that there was a fundamental flaw in the evidence on which the Thai court convicted the women, sentencing Smith, then aged 18, to 25 years' and 17-year-old Cahill, to 17 years' jail .
It was alleged in court that 21 bags of high-grade heroin were discovered in a dozen shampoo and soap bottles and nine sweet and drink-powder tins found in their suitcases at Bangkok International Airport on 18 July 1990.
The total weight of the alleged heroin haul was put at 30.5kg, worth about pounds 4m in street-value.
Dr Gough said that quantity of heroin would have required 21 containers holding an average of 2.9 litres each - the equivalent of at least 30 two- litre bottles.
However, the Thai police testifiedthey found the drugs in shampoo bottles and tins with a capacity of no more than 1.3 litres. It was further claimed that the heroin was found in plastic cylinders welded into the containers - which would have considerably reduced their capacity.
According to Dr Gough, if the containers had a 1.3-litre capacity, 'a minimum of 47 such bottles will be needed to accommodate 30.5kg of heroin'.
It would have been possible to conceal the heroin in the alleged 21 containers - if the drug had been heavily compressed into slabs. However, press photographs taken at the airport - before the 'find' - and the court's own recorded judgment, showed that the evidence related to 21 bags of 'white powder'. There was no mention, or display, of slabs of heroin.
The only exhibit produced during the trial was one of two suitcases. Neither the heroin nor the containers were produced in court.
Mr Jakobi said that it had been reported since the trial that Thailand's 1979 Narcotics Act created a system of rewards for police and their informers, related to the value of the drugs found, on conviction of smugglers.
Yet in spite of the scale of the haul in the Smith- Cahill case, a reward of only pounds 2,000 had been paid; well below the legally-fixed rate.Reuse content