Animal experimenters in the US, beware: you may find yourselves facing criminal charges for simply doing your job. That’s what has happened to nine staff at the University of Wisconsin-Madison, who could go to jail or pay heavy fines for carrying out decompression experiments on sheep for the US navy.

Some sheep died in the experiments, which aimed to find new ways to save divers from decompression sickness, otherwise known as “the bends”. Antivivisectionists at the Alliance for Animals in Madison and at People for the Ethical Treatment of Animals discovered that Wisconsin has a law banning the killing of animals through decompression.

The AFA and PETA filed charges, and on 2 June circuit judge Amy Smith backed the animal-rights groups’ claim. She concluded that the researchers “intentionally or negligently violated Wisconsin law”, and so should face criminal charges. Smith dismissed the university’s defence that the research project was exempt from the law.

The case is the first in which animal researchers have faced criminal charges in the US since 1981. “If animal rights groups continue to pursue the use of laws in ways they were not originally intended, I’m concerned that universities may be forced to expend additional resources to counteract these unwarranted legal attacks,” says Frankie Trull, president of the Foundation for Biomedical Research in Washington DC, which defends animal experiments.

“I recommend institutions doing biomedical research educate their in-house counsels about these animal rights strategies and be prepared.”