A woman in the US is reported to have lost $400,000 (£270,000) after falling under the spell of one of the most extraordinary Nigerian 419 scams ever uncovered.

Janella Spears, who lives in Oregon, is said to have sent the eye-watering sums to criminals over a two-year period, mostly in amounts in the low thousands, after being contacted in a spam email by criminals offering her a cut of a $20.5 million fortune.

There was no fortune, of course, but that didn't stop Spears from reportedly spending her husband's retirement income, borrowing money against the family car and remortgaging the house, in the hope that the scam might turn out to be genuine.

The scammers even claimed at one point that President Bush and FBI Director Robert Mueller were involved. The case only came to light when Oregon Department of Justice officials noticed one payment for $144,000 being wired to Nigeria, and traced it to Spears.

After raiding her home, and studying a long chain of email correspondence, Spears was warned not to send further funds, which could constitute collaborating with criminals, however unwittingly.

"As a reverend and an American, I just wasn't prepared for that level of dishonesty," Spears told a local Oregon newspaper.

"What's impressed the police the most about this is the level of professionalism these scam artists have," she was quoted as saying.

To speculate, it is not entirely clear to what extent Spears was genuinely gullible or just 'hooked' in an addictive way to the lures used to take money from her, but the case raises interesting questions about the true nature of such crimes. Are the small but profitable number of people who continue to fall for these scams really naïve or perhaps just addicted to the thrill of risk?

Even by the terrible standards of a scam named after section 419 of the Nigerian penal code, the case sets new benchmarks in size, long-term embezzlement, and the involvement of the victim against her better judgement.

The 419 has a long history, and has remained remarkably consistent in its use of implausible lures over the years. It seems able to find victims despite widespread publicity.

Deviations from the usual 'dictator attempting to get funds out of an African country' are relatively rare. In 2006, the then Scottish Minister for Culture, Tourism and Sport, Patricia Ferguson, was used in one reported 419 email, while only this week an Australian member of Facebook reported being contacted by a person known to her asking for the modest sum of $500. The request was bogus, the result of a clever form of ID theft.