Jeffrey Wigand has begun spilling the beans, and America's hitherto impregnable cigarette manufacturers have begun to tremble. As the Attorney-General of Mississippi asserts, "Mr Wigand's testimony is going to be devastating for the tobacco industry."
This week, after an extraordinary legal tug of war, the 52-year-old former research chief of the Brown & Williamson company answered a subpoena and went to Pascagoula, on the Gulf of Mexico, to give a first deposition in a benchmark case brought by Mississippi. The state wants to recover taxpayers' money spent on treating diseases caused by cigarettes.
At first glance Mr Wigand cuts an unlikely figure as the man who may change the course of America's tobacco wars - a biochemist and highly regarded manager in the chemical and drug industries before he joined B&W, a subsidiary of BAT Industries of Britain, in 1989 at a salary of $300,000 (pounds 200,000). Four years later he was sacked, and today earns barely $30,000 teaching science and Japanese at a high school in Louisville, Kentucky. But to the tobacco companies he is the ultimate nightmare: the highest ranking, most strategically placed operative ever to defect to the enemy, the man who knows the secrets.
These are rough legal times for the industry. In Louisiana, a huge class- action suit which theoretically could embrace most of the country's 50 million smokers charges it with concealing the knowledge that smoking was dangerous. Five other states plan to follow Mississippi's example and seek reimbursement of hundreds of millions of Medicaid dollars disbursed on those suffering from smoking-related illnesses.
The federal government, which is trying to regulate tobacco as a drug, is investigating whether in the 1980s the industry breached anti-trust laws by conspiring to stop development of a safer cigarette. In three separate but overlapping battles Mr Wigand is pivotal, with assertions that the companies have known for decades of the harm caused by smoking.
This week in Pascagoula, his testimony was heard by state and federal lawyers. Although it has been temporarily sealed by a judge, it is expected to be made available for the class-action case. It represents the most dangerous court challenge yet to an industry which boasts it has never paid a cent of damages in a lawsuit. Cancellation by CBS of an interview with Mr Wigand for fear of litigation by B&W demonstrates the industry's power, but this may well prove ephemeral.
Already the transcript has been leaked of the CBS interview, in which he accuses B&W of using Coumarin, a dangerous and possibly cancer-causing ingredient, to enhance the flavour of pipe tobacco. He also says the company stifled research into safer cigarettes.
Having successfully threatened to sue CBS, the company took legal action against its former executive, claiming that the interview and any future court testimony would breach a confidentiality pledge he gave B&W in 1993. A court in Louisville upheld that, but a judge in Pascagoula overturned it, saying Kentucky law had no standing in Mississippi.