Swiss court rules all people with HIV can be criminally liable for transmission, even if untested

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Switzerland's highest court - the Federal Court in Lausanne - has ruled that a man who was unaware of his infection when he had unprotected sex that transmitted HIV is still criminally liable. The ruling suggests that unprotected sex in Switzerland without first disclosing a sexual history may result in prosecution should HIV be transmitted.

In 2006, the California state Supreme Court ruled that ‘constructive knowledge’ – when it is reasonably foreseen by a reasonably intelligent person that their actions could lead to harm – of the possibility that HIV transmission may occur, is enough to allow for civil liability. However, this is the first ruling anywhere in the world to find that an undiagnosed individual may be criminally liable for HIV transmission.

The criminal case, reported in some detail in the July 1st edition of the Neue Zürcher Zeitung, began with a trial in Zurich’s District Court in 2005. The complainant was a woman who had tested HIV-positive after having unprotected sex in 2002 with the defendant. Although the man had not been diagnosed HIV-positive before their sexual encounters, he did have a history of unprotected sex.


phylogenetic analysis

The comparison of the genetic sequence of the virus in different individuals in order to determine the likelihood that two or more samples are related. This involves creating a hypothetical diagram (known as a phylogenetic tree) that estimates how closely related the samples of HIV taken from different individuals are. Phylogenetic analysis is not a reliable way to prove that one individual has infected another, but may identify transmission clusters, which can be useful for public health interventions.


A patient’s agreement to take a test or a treatment. In medical ethics, an adult who has mental capacity always has the right to refuse. 

informed consent

A patient’s agreement to continue with a clinical trial, a treatment or a diagnostic test after having received a full written or verbal explanation of the risks, benefits and the possible alternatives. 


A variant characterised by a specific genotype.



The transition period from infection with HIV to the detectable presence of HIV antibodies in the blood. When seroconversion occurs (usually within a few weeks of infection), the result of an HIV antibody test changes from HIV negative to HIV positive. Seroconversion may be accompanied with flu-like symptoms.


Notably, in 2000, he had been informed by a former sexual partner that she had been diagnosed HIV-positive. The man testified that he had not taken an HIV antibody test because he did not believe himself to have been infected during unprotected sex with this woman, based on a lack of seroconversion symptoms at the time. However, the District Court found him guilty under both public health and criminal law.

Swiss criminal HIV exposure and transmission laws

Liability for HIV exposure or transmission in Switzerland is based on two distinct sets of laws – those aimed at protecting the general public (public health law) and those protecting the individual (criminal law).

Article 231 of the Swiss Criminal Code allows prosecution by the police – without the need for a complainant – of anyone who “deliberately spreads a dangerous transmissible human disease.” Informed consent to unprotected sex does not nullify the offence, and even the attempt to spread a dangerous transmissible human disease (i.e. HIV exposure without transmission) is also liable to prosecution.

Article 122, also allows prosecution for grievous bodily harm if unprotected sex results in HIV transmission. However, informed consent is a defence in this case, and a prosecution requires a complainant in order to prove that informed consent (i.e. disclosure of HIV status before sex) was not obtained.

In effect, “any unprotected sex of an HIV-positive person is a crime, even if there is no transmission,” Professor Pietro Vernazza, of the Cantonal Hospital in St. Gallen, and President of the Swiss Federal Commission for HIV / AIDS, tells In part, it was these draconian laws that motivated the Swiss Federal AIDS Commission’s recent statement regarding antiretroviral therapy’s effect on HIV transmission.

Cantonal Court upholds appeal

The undiagnosed man convicted under these laws appealed to the Zurich Cantonal Court in 2007. The appeal had two parts: questioning whether an undiagnosed person has a legal requirement to test for HIV and to disclose their sexual history; and questioning the validityof the phylogenetic analysis evidence used in the original case.

The Cantonal Court ruled that not only was he not liable – because there is no law mandating HIV testing or disclosure after unprotected sex – but also that the scientific evidence was not conclusive enough to prove that he had infected the complainant.

Although phylogenetic analysis of the samples linked the man's rare HIV subtype to the complainant’s own HIV strain, his lawyers successfully argued that phylogenetic analysis cannot rule out that another individual may have infected the complainant. In addition, phylogenetic analysis ruled out a link between the defendant and the HIV-positive woman with whom he had ‘risky’ sex in 2000.

Federal Court reverses appeal

On June 30th 2008, Switzerland's highest court ruled that the man can be held responsible for HIV transmission under both public health and criminal law. They said the defendant could not ignore the fact that his own past behaviour was risky, particularly since one of his previous partners had told him she was HIV-positive after they had had unprotected sex.

It also ruled that the woman did not have joint responsibility for her HIV infection because she did not give informed consent to the risk of unprotected sex. If she had known the man’s sexual history, it was unlikely she would have had consented to unprotected sex, it said.

An unofficial translation of the German-language article in the Neue Zürcher Zeitung quotes the following: “ have to refrain from having unprotected intercourse, if there are concrete indications for a potential HIV infection. Indications can be, in principle, any perceived risky contact in the past, such as unprotected intimate contacts with a person whose sexual past one does not know. In principle the Safer Sex Guidelines of the Federal Health Office are authoritative for this. Irrelevant are the statistical risks of transmission or the fact that signs [of seroconversion] failed to appear.”

The Federal Court also overturned the ruling on phylogenetic analysis, saying that since the defendant’s strain was so rare, it would have been highly unlikely that the complainant could have acquired it elsewhere.

In effect, Switzerland’s highest court had now ruled that anyone who has had unprotected sex in the past, and does not disclose it to their sexual partner before having unprotected sex with them, may be criminally liable should HIV transmission take place.