On May 11 2004 Steve Kurtz awoke to find his wife dead beside him. He would come to refer to this date as "5/11"; it was the day his life took a Kafkaesque turn. When paramedics arrived at his house in Buffalo, New York State, they noticed a makeshift laboratory on an upstairs landing, with an incubator full of toxic-looking bacteria, and alerted the police.  Kurtz assured them his lab was, in effect, his studio; that he was an internationally recognised artist, as well as an art professor at the University at Buffalo, who used molecular biology in his work. He was forced to give the police an impromptu presentation while Hope lay dead in another room - he even stuck his finger in a Petri dish of bright scarlet bacteria and tasted it to prove it was harmless. "They thought I'd germed her to death," Kurtz says. An autopsy later showed that Hope, his partner of 27 years, had died of heart failure in her sleep.  The day after the death, however, when Kurtz returned from the funeral home, three car-loads of FBI agents were waiting for him. He was now suspected of bio-terrorism. His house was quarantined with yellow police tape. In what became a media spectacle ("Bioterrorism Blunder?" asked NBC news), five regional branches of the FBI, the Joint Terrorism Task Force, the Department of Homeland Security, the Department of Defence, the Buffalo police, fire department, and state marshall's office swarmed over Kurtz's home. They were protected by white chemical suits and wore breathing apparatus. In the middle of all this, his next-door neighbour put up a sign of support in the window: "He's not a terrorist, he's my neighbour!"  I meet Steve Kurtz, now 47, at the "crime scene", where he's offered to put me up for the night. "You're staying in the rock'n'roll bed," Kurtz says, gesturing towards a mattress in the hallway. "Henry Rollins, Kim Gordon of Sonic Youth, Circle Jerks' Keith Morris, and someone from the Bad Brains have slept in it." It's after midday, and he has just woken up. His curtains are perpetually drawn and from the street you can see that his bedroom windows are covered in silver foil. "The FBI made such a big deal about it," he says of the foil. "It's because I sleep in the daytime - I need the room really dark. I asked my probation officer, 'What the hell were they thinking?' And she was like, 'You ever hear of curtains? It's just not normal!'"  Last June a federal grand jury was convened to evaluate bio-terrorism charges against Kurtz. He was indicted, but not under the biological weapons anti-terrorism act. He and Robert Ferrell, a professor of human genetics at the University of Pittsburgh, were charged with mail and wire fraud, accused of colluding to illegally furnish Kurtz with $256 (£146) of harmless bacterial cultures. The crime carries a sentence of up to 20 years. Kurtz's lawyer, Paul Cambria (who defended pornographer Larry Flynt against obscenity charges), is arguing the case should be thrown out of court. The government's "paranoid over-reaction" is, he says, a political attack on Kurtz's subversive art.  The artistic community has rallied to the cause, staging protests and organising an auction - with work donated by 50 artists, including Richard Serra, Hans Haacke, Cindy Sherman, Mike Kelly and Sol LeWitt - that raised $170,000 (£97,000) for his defence. His case has not yet come to trial but Kurtz has already become, as the New York Times put it, "an unlikely art world martyr-hero". Perhaps, as a sticker on his fridge puts it, he might be better described as a "prisoner of art".  In 1986, Kurtz and his wife co-founded Critical Art Ensemble (CAE), a small artists' collective "dedicated to exploring the intersections between art, technology, radical politics and critical theory". Their work is often mistakenly lumped in with the emerging field of bio-art, which fuses art and science, messing with DNA to spawn Frankensteinian aberrations, such as a rabbit that glows a fluorescent green thanks to a gene isolated from jellyfish.  Kurtz, a self-taught scientist, is keen to distance CAE from these stunts. "What we're interested in is the political economy of biotechnology," he says. In a project titled Free Range Grains, CAE set up a DNA extraction laboratory in a museum and invited people to bring along food for testing, to see if it was contaminated with genetically modified organisms. Almost everything was, so the group created "defence kits" for those who felt they were "having the GM revolution forced upon them". They obtained copies of the patents to one of Monsanto's pesticide-resistant plants and devised a way in which this resistance could be destroyed using a supplement available from health food shops. "This was probably where we crossed the line," Kurtz reflects.  In CAE's most recent manifesto, Molecular Invasion, Kurtz encourages his readers to carry out other acts of "fuzzy biological sabotage". "The fuzzy saboteur," the book declares, "has to stand on that ambiguous line between the legal and the illegal (both criminally and civilly), in areas that have not yet been fully regulated." The reader is advised to avoid direct sabotage, such as arson, in favour of "pranks". Cues are taken from the CIA - their lacing of Fidel Castro's cigars with LSD is considered model behaviour. One idea is to release genetically mutated and deformed flies in biotech research facilities and nearby restaurants to stir up paranoia.  When the FBI raided his house, Kurtz was researching the history of germ warfare for a new project. He was growing simple types of bacterial cultures, routinely used in high-school biology classes, that could also be used to simulate the mushrooming of anthrax and plague. (CAE recently came to Britain to simulate, with a pontoon-load of guinea pigs, an unsuccessful bio-weapons test conducted off the Isle of Lewis in the early 1950s.) Kurtz is interested in how ineffective chemical weapons are - how useless as a terrorist tool. Last year Bush allocated $5.9bn to bio-terrorism defence. Kurtz points out that only five people died of anthrax poisoning in the 2001 scare (the FBI traced that particular strain of anthrax to a US Army lab at Fort Detrick) but the incident has been exploited to create an all-pervasive fear.  The FBI detained Kurtz in a hotel; agents took the room across the hall so they could watch his door. The local bureaus of the FBI and Joint Terrorism Task Force had just been given medals for tracking down the "Buffalo six", a gang of Yemeni teenagers who had visited an al-Qaida training camp in Afghanistan and who were thought to form a sleeper cell. "One by one," Bush said after the arrests, "we're hunting the killers down." They thought that with Kurtz they'd hit the jackpot again.  Investigators impounded Kurtz's three computers, the contents of his lab, his car, correspondence and a small library of books with titles like Spores, Plagues and History: The Story of Anthrax. They locked his cat in the attic for two days without food or water - you can still see the scratch marks on the door. "They thought I might be using the cat to spread plague," Kurtz explains.  They also confiscated his wife's body. Hope's ashes now sit on the mantelpiece in Kurtz's study. "They still have bits of her," Kurtz says. "They've got hair and blood samples. I'm going to try and get the last bits of her back as soon as this is over."  The political climate in America has been described as a new McCarthyism. "The only thing that is different," Kurtz agrees, "is that they won't admit it's McCarthyism. They say, 'This has nothing to do with ideology. We never thought about what political persuasion Kurtz had - he's just a common criminal.' McCarthy said we should have political prisoners. Now they're saying: we don't have political prisoners, we're just protecting the public."  Kurtz shows me his laboratory, a trestle table covered with pipettes, bottles of chemicals and Petri dishes. "This is what got me in all that trouble," he says as he opens the door of an incubator and removes a dish covered in a bright red smear of Serratia marcescens. I instinctively recoil. "It's not really the bacteria that stinks so much," he says. "It's the agar. The FBI thought they were slick, but they missed one of my tubes of it. So I still have the original sample."  We have dinner at a nearby restaurant with Kurtz's new girlfriend, Lucia Sommer, who is part of a "cyberfeminist" art collective and was a friend of Hope's. On the way there someone recognises him in the street: "Good luck, man!" the stranger says. Sommer tells me some teenagers once stopped Kurtz and said: "You're infamous, aren't you? Well, to us, you'll always be famous."  Over some steak Kurtz tells me that his persecutors "have to have something to show for the millions of dollars they've spent on this. They're trying to create a kind of hysteria, a horrible kind of vigilantism. It's right out of Hitler's handbook. The final goal is to silence and intimidate voices of dissent." If he wins his case, Kurtz is going to use the money from his defence fund to try to free the Buffalo six, whom he feels have been wrongly imprisoned, or to set up a fund for artists facing similar legal troubles. There will, he believes, be many more.  Several hours of vodka and critical theory later, we find ourselves back on the sofa where we began. It's four in the morning by the time Kurtz tells me: "I don't remember those first six months. I have little vague fragments here and there. I can remember the couple of days when Hope died and I went into detention - and after that it's kind of gone. I think that's a period of my life that's just lost.  "At the beginning when there was no money, and there were lawyers' bills, I was under way too much stress. My blood pressure went through the roof and I had to go on medicine, but I'm off all that now. I'm pretty much back to normal." His co-defendant, Robert Ferrell, who was being treated for cancer when he was indicted, has since suffered two strokes. "I think they're going to kill him," Kurtz sighs.  He tells me that he thinks his phone is tapped, that his emails have been read, and a few times he's caught someone tailing him. Someone whom he suspects was an undercover agent asked him if he'd like to kill the president. Does all this make him paranoid? "Their whole thing," he says, "is to make people freaked and stressed out and paranoid. Their brains are going to melt down and they're going to do something they shouldn't.  "But," he adds, "you have to go about your life as though they're not there, otherwise you'd just go crazy".
Steve Kurtz was just another subversive US artist - until the FBI accused him of bio-terrorism. He tells Christopher Turner why he won't be silenced.