By Michelle Roberts
Health reporter, BBC News
Condoms can stop HIV transmission
There have been a number of high profile cases recently where people have been prosecuted for passing on HIV, with sentences ranging from a small fine to imprisonment.
In August 2006, a gay man being accused of 'recklessly' passing on the virus to his partner became the first person in Britain to be acquitted of such a crime.
These cases have thrown up a host of questions - medical, legal and ethical.
Some condone the prosecutions, saying they bring justice and act as a deterrent.
Others argue criminalising transmission increases stigma, discourages people from getting tested and could drive the Aids epidemic underground.
The Crown Prosecution Service is seeking public opinion on the way in which it deals with cases involving the intentional or reckless sexual transmission of infections which cause grievous bodily harm.
Seamus Taylor, director of equality and diversity at the CPS, explained: "We wish to set out our position clearly as we want to promote greater confidence in the criminal justice system."
In particular, the CPS is asking if the context in which the sexual behaviour occurred should be a relevant factor when determining whether it is in the public interest to prosecute.
And what weight, if any, should be given to the defendant's ability to ensure a condom is used?
The recent acquittal shows existing scientific tests cannot prove direct transmission from one particular person to another.
The prosecuting man was having sex with more than one person infected with the virus and test results could not show conclusively which of his partners had given him HIV.
HOW HIV CAN BE PASSED ON
Fact: Blood, semen, vaginal fluids including menstrual blood, breast milk
Fiction: Saliva, sweat, urine, through skin, through air
Fact: Sex without a condom, injecting drug use, mother to baby, organ transplant
Fiction: Kissing, holding hands, sharing a drink
Dr Anna-Maria Geretti, a consultant clinical virologist at the Royal Free Hospital in London who testified at the trial, said cases should not be based on virological evidence alone.
"It can show whether two people are infected with a similar virus, but that does not prove that person A gave it to person B.
"There could be a chain of transmission where four or five people are infected with a similar virus."
Practically, it can be hard to trace contacts, as people will often not have contact details of everyone they may have slept with in the past.
And if someone is being accused of reckless transmission, it is unlikely that they will want past partners to be contacted, in case it makes their situation worse.
Even if you could prove precisely who had transmitted the virus, the question of intent remains.
None of the convictions to date have been for deliberate transmission. The charges have been for "reckless grievous bodily harm", under the Offences Against the Person Act of 1861.
Mr Dica was given a prison sentence for transmitting HIV to two women
The only requirements for a successful prosecution under this charge is that someone with HIV has sex, fails to tell their partner their status, and during that sex passes their virus on.
Aids charities generally agree that it is correct and acceptable to prosecute anyone who intentionally infects another with HIV.
However, they believe prosecutions for "reckless transmission" are wrong and that transmitting HIV in this context is not criminal.
The Terrence Higgins Trust says that in the vast majority of cases of onward transmission, people with HIV do not pass on the virus intentionally.
But Daniel Sokol, medical ethicist at the Imperial College Faculty of Medicine, London, says, morally, this is no defence.
"Even if there is no intent to cause harm at all, the person can still be blamed morally if he could have reasonably have expected to have put the partner at risk or if he should have known.
"He has a duty to be informed about his condition and its transmitability.
"We can still criticise a reckless driver even if he didn't intend to cause any trouble and didn't know he had too much to drink. Ignorance is not enough to get us off the moral hook."
Lisa Power, a spokeswoman for the Terrence Higgins Trust said that often transmission occurs as a the result of sexual partners jointly failing to choose to practice safer sex.
In other cases, a condom may have been used but have split.
She pointed out that some people might not know if they were HIV-positive. Others might find it extremely difficult to disclose their HIV status.
Many people have difficulty coming to terms with having HIV and remain in denial. Fear of rejection and stigma can also prevent people from being honest, she said.
And there is no guarantee that disclosure of HIV-positive status will remain confidential with the partner.
"Negotiations in the bedroom are very complicated and often not completely verbal," she explained.
"There is plenty of research to show that amongst gay men at least, those living with HIV assume that not using condoms means the other person is positive too, whereas negative people assume not using condoms means the other person is negative.
"Often people have sex in the heat of the moment and under the influence of alcohol and may not do what they would do when they were sober."
Equity and public health
Bonita de Boer of Avert said: "People transmit all kinds of other sexually transmitted infections within relationships that never get criminalised.
"There needs to be a line drawn somewhere on what is criminal and what is not. At present, there are no guidelines on this issue, and courts are relying on a law that is well over 100 years old to obtain convictions.
"This needs to be addressed before prosecutions in this country start snowballing."
HIV charities warn that criminal prosecutions could actually increase transmission rates, by deterring people from getting tested for HIV and disclosing their HIV status to sexual partners.
A spokeswoman from the National Aids Trust said: "Criminalising of reckless transmission is going to run counter to public health objectives which emphasise personal responsibility for sexual health, increased testing amongst vulnerable groups and an end to HIV-related stigma and discrimination."