Sir

In your recent Opinion article on when experiments with non-human primates can be justified (Nature 417, 684–687, 2002), a relevant perspective can be found in US constitutional law. A non-human primate can be regarded as belonging to the 'quasi-person' class originally used in 1865 to define African-Americans, who were not accorded full constitutional personhood in law, but were entitled to some natural rights under the US constitution, including that of self-interest (see R. M. Lebovitz, St Thomas Law Review, 14, 561–600; 2002). But does this mean that primates are entitled constitutionally to be free from the physical abuse produced by experimentation?

No constitutional right is absolute, but there must be an important and persuasive reason for abrogating it. In the United States, a person's so-called 'liberty interest' is a fundamental constitutional right, yet the government can infringe upon it when the circumstances are important enough. A famous example is an early twentieth century case in which an adult man refused to be vaccinated against smallpox, despite a Massachusetts state law requiring it. The case made its way to the US Supreme Court, where the justices wrote that constitutional rights are not unencumbered, but may be infringed when necessary for the good of the community, including for reasons of public safety to protect the population from a disease epidemic (Jacobson vs Massachusetts, 197 US 11; 1905).

Using the same rationale, it can be argued that, although most animal experimentation is not significant enough to warrant violating a primate's right of self-interest, some experimentation may meet this high standard. For instance, research on a particular vaccine may be important enough as a societal concern to excuse intrusion on the animal's right of self-interest. We must carefully scrutinize the goals of experimentation to determine when it justifies extinguishing a US animal's constitutional right of self-interest.