It is believed to be the first time that genetic information on HIV has been used as forensic evidence. Lawyers say that it could lead to a flood of cases in which HIV positive people take some form of action against the person they say infected them, using such data to support their case.
They say that some people in Britain are thinking in terms of 'individual redress', mirroring the American trend in HIV litigation.
Dr Andrew Leigh Brown, head of the Centre for HIV Research at Edinburgh University, the country's leading laboratory for genetic studies of HIV, says he has already been consulted by a British lawyer who is considering using viral genetic information on behalf of a client.
Graham Ross, the solicitor who co-ordinated the successful action against the Government on behalf of HIV-infected haemophiliacs, said the data would be important if British cases ever came to court. 'I really don't see why not, if forensically it was possible to establish a link between the people who were infected.' A court would require that 'probability' of transmission to be more than 50 per cent, he said.
In the Swedish case, which is reported in today's issue of Nature, the man had been convicted of rape and deliberate transmission of HIV.
The case went to the court of appeal and a genetic analysis of the strains of HIV carried by the rapist and his victim was carried out. Based on this genetic analysis and other evidence, the verdict was upheld.
Dr Leigh Brown and colleagues at Edinburgh have carried out similar analysis of viral strains from different individuals to see if they were related.
This included the highly publicised case of the Florida dentist who died of Aids. He was shown to have infected at least three of his patients with HIV 'beyond reasonable doubt', but the evidence was not used because the case was settled out of court.
Dr Leigh Brown said that his department would not take on any private cases because 'people's view of these investigations have been strongly influenced by the use of genetic fingerprinting techniques (using blood and semen for example) in court cases.
'Their expectations are jumping ahead. We are much less confident in these results than we would be in genetic fingerprinting,' he said.
For an individual to transmit the virus knowingly is a criminal offence in some countries including Sweden, Australia and the US. At least 200 lawsuits involving the transmission of HIV have been filed in the US by HIV positive people against the person who is claimed to have infected them.
The use of viral genetic evidence will figure in several of these cases, according to Larry Gostin, director of the US Aids Litigation Project at Harvard.
Kenneth Clarke, the Home Secretary, ruled out legislation on HIV transmission in Britain last December.
This followed the case of the West Midlands haemophiliac who had unprotected sex with several women despite being HIV positive.