It all started on a runway in San Antonio, Texas. Martha Stewart was being characteristically gracious to the two female friends flying with her on her private jet to a holiday in Mexico; a fragrant graciousness, after all, was her stock-in-trade and what had made her famous and rich. The date was 27 December 2001, and for breakfast on the jet they had champagne, caviar, foie gras and fresh Melba toast. On a stopover at San Antonio airport, Martha Stewart then made a phone call at 1.31pm - and it is what was said in that phone call that has led Stewart to face 30 years in prison and fines of up to $1.25m.

To millions of American women, Martha Stewart is the domestic goddess to end all domestic goddesses. What she teaches them is how to be yes, gracious - a notion of class gentility that tends to strike a note among middle-aged women with nothing better to do than consume Stewart's multifarious self-improvement programmes and products. Everything is domestically perfect in Martha Stewart's world; her zillions of disciples believe that if you follow Martha's rules, you can achieve perfection in your domesticity and, in particular, in your entertaining.

Hers is, indeed, a quintessentially American story. She was born Martha Kostyra 62 years ago in New Jersey, the second of a Polish-American family of six children; mother was a teacher and father a pharmaceuticals salesman. Mother supposedly initiated the young Martha in all the domestic duties of womanhood of the time, in cooking, baking and sewing; father taught her the tricks of gardening and how to repair domestic gadgets that had gone on the blink. Martha made it to Barnard College, a women's offshoot of Columbia University. From there she launched a successful modelling career, appearing in television commercials for cigarettes and for Lifebuoy soap, among other products. In 1965, her daughter was born; two years later, she began a successful second career as a stockbroker. She and her husband (from whom she has since been divorced) bought an 1805 farmhouse in Connecticut named Turkey Hill, from which her empire mushroomed.

Before long, there was no looking back for our Martha. In 1976, she started a catering business run from the basement of her farmhouse; within ten years it had a turnover of more than $1m. In 1982, she brought out the first of many lavishly illustrated coffee-table books. Entertaining made her a one-woman industry, soon to morph into television programmes, videotapes, CDs of gracious dinner music with which to entertain graciously, television specials - and dozens of books on hors d'oeuvres, pies, weddings, gardening and even restoring old houses. Her own magazine, Martha Stewart Living, eventually had a circulation of 2.3 million, dispensing advice on everything from Christmas decorations to childcare.

In short, a spurious paradise and perfection was what she marketed - and did so brilliantly. Her company is now known as Martha Stewart Living Omnimedia, Inc - and when it went public in 1999, it supposedly made Martha a billionaire. She persisted with that image ("Jane Austen is a mentor of mine, in terms of language"), which really transcended all known human bounds in terms of achievement ("I read everything from all the Europeans, the Russians, the English novelists"). By pursuing that self-image of infallibility ("You know, when most people are sleeping it's hard to be up and around, so I read"), she made millions of American women hang on her every word - in the vain hope that they, too, could one day be perfect and infallible like her.

This abruptly changed on that December morning. If we are to believe evidence put before a New York federal court in recent days, a colourful, 28-year-old assistant with the Merrill Lynch company of stockbrokers named Douglas Faneuil told her that the chairman of a pharmaceutical company, ImClone Systems, was selling his stock in his company: he had heard that the US Food and Drug Administration (FDA) was going to come out with a bad report on Erbitux, which had been thought to be a successful anti-cancer drug that would boost the fortunes of the company.

Martha then had 3,928 shares in ImClone worth $58.43 each, or a total of $229,513. She supposedly gave the order that day to Faneuil to sell them - before news of the chairman selling his stock, or the bad news about the anti-cancer drug, came out. The former chairman's name is Samuel Waksal, he is a chum of Martha's, and he himself is now serving seven years for insider trading, having admitted that he had inside knowledge of the bad FDA report that was to come.

If she had waited until the following day - when all the privileged news was made public - she would have sold stock that had slipped to $45.39. That would have meant she would have incurred a loss of $51,222 - chicken feed for her.

But in an era of the Enron, Tyco and Parmalat scandals, it was enough to set the prosecutorial dogs on her; she is, after all, one of the few self-made women in America to have reached such rarefied financial heights. Although Martha is alleged to have engaged in insider trading, she is not actually charged with that: the charges against her include conspiracy, obstruction of justice and securities fraud. She is also alleged to have lied to the stockholders of her own company to keep it buoyant. Together, she has been indicted on nine criminal counts.

Martha claims that she had an arrangement with her stockbroker to sell her ImClone stock if its share value fell below $60 - a not-altogether-convincing claim, given that she could have had a "stop-loss order" on her ImClone stock that would not have required her intervention from the tarmac of San Antonio airport. She is now facing a female judge and a mainly black jury of eight women and four men.

The other side to Martha's nature has now come out. In private, she is no genteel lady but - according to a biography of her - a calculating shrew who treads ruthlessly on people who get in her way. She has a hot temper, supposedly dismissing Faneuil as "a little shit". Not very gracious stuff there. Last Tuesday, her secretary testified that Martha had started to change the record of that fateful phone call, but then mysteriously changed her mind. Whether she will take the stand herself remains the question all Martha watchers are now asking with bated breath.

Yet I am sure I'm not the only person who feels rather sorry for Martha. When American prosecutors go after someone, they want to hang, draw and quarter their prey: and it is hard to see her alleged transgression as wicked enough to merit 30 years in prison.

Indeed, she markets a phoney gentility that I find far more offensive than her supposed criminal share shenanigans. But does that make her a hardened criminal? No, in my opinion: but, coming from that humble Polish-American background, she is a woman who has lived the American dream and made a billion bucks. And for that very reason, those prosecutorial wolves are now determined to pull her down from that so-gracious pedestal of hers.