The TV host who thinks everybody's guilty

Nancy Grace's commitment to convicting any defendant who comes before a jury has won her million of viewers

Tears, cheers, and by all accounts a jolly good party took place when Amanda Knox returned home to Seattle this week.

"Welcome Home" banners dangled from her doorstep, balloons filled her family home, and a nationalistic fervour gripped the US media.

There is, however, one corner of American pop culture where no accused criminal is ever considered to be entirely innocent – a simple place where police officers are always right, prosecutors never over-egg puddings, and butchered evidence simply does not exist.

That place is whatever TV studio happens to be occupied by Nancy Grace, an astonishingly popular television host who fronts an evening talk show on HLN, or "Headline News," a tabloid-friendly sister channel to the blue-chip cable news outlet CNN.

"I am very disturbed, because I think it is a huge miscarriage of justice," she said of this week's events. "While Amanda Knox did not wield the knife herself, I think that she was there, with her boyfriend, and that he did the deed, and that she egged him on. That's what I think happened."

The comments blithely ignored the absence of concrete evidence tying Ms Knox to the murder of Meredith Kercher. They paid no heed to revelations about contaminated DNA and inept police work which this week saw her acquitted, after four years in an Italian prison.

But that's how Grace rolls. Each evening, the small but energetic 51-year-old works herself up into a state of vein-popping outrage in order to pass comment on whatever news events lurch across her dimly illuminated horizon.

Sometimes Grace, a self-styled "victim's rights" activist and former prosecutor, turns her howitzers on fellow hosts. Other times, she lays into studio guests. More regularly, she attacks the court system and legal establishment. But her favourite target for vituperative rage is the accused.

Earlier this summer, a jury in Florida delivered a verdict of "not guilty" against Casey Anthony, a mother accused of killing her two-year-old daughter. That night, Grace looked her viewers sternly in the eye. "The devil is dancing tonight!" she declared.

That pantomime display earned an audience of three million viewers, according to the ratings agency Nielsen. It represented a personal high for Grace, who has been broadcasting for around a decade, and was the highest viewing figure in HLN's 29-year history.

More recently, Grace confidently declared that Conrad Murray, the private doctor accused of the involuntary manslaughter of Michael Jackson, "will be doing jail time". She said: "You can't just walk into a California mansion and kill the King of Pop!"

Such statements would be illegal in the UK, where it is illegal to risk prejudicing an ongoing court case. And they help to explain why Michael Pastor, the judge in Dr Murray's trial, has repeatedly warned jurors to avoid the news media for the duration of proceedings.

He isn't the only legal professional concerned by Grace's impact on high-profile proceedings. There are widespread fears that the popularity of her stock-in-trade is threatening the impartiality of jurors, and fuelling a lynch-mob mentality among the public.

"Grace is the Madame DeFarge of American justice," says Jonathan Turley, a professor of law at George Washington University. "She refuses to undo her knitting even in the face of reasonable doubt or compelling evidence. Her snarling, retributive style is the draw for a very sad and very angry portion of our population."

Jane Kirtley, a professor of media ethics and law at Minnesota University, believes that Grace's apparent disdain for the presumption of innocence is "particularly irresponsible," given that she spent the early years of her career as a lawyer.

"She is not a disinterested observer, ever," Ms Kirtley says. "She always, always, always takes the side of the prosecution or victim. She chooses whatever cases are high-profile and says 'guilty guilty guilty'... There's a bloodthirstiness to people and Nancy Grace is artful in pandering to that. I find it sad that someone who exploits our very worst instincts is so very successful."

Grace claims that her tough-on-crime mentality is rooted in personal heartbreak. She often recounts how she decided to become a lawyer and later public prosecutor at 19, after a then-fiancé called Keith Griffin was murdered. However when the New York Observer attempted to fact-check that story, in 2001, it found that key passages had been exaggerated or falsified.

Ms Grace responded to their findings by saying that she had misremembered details of the episode because: "I have tried not to think about it."

More recently, she found herself at the centre of controversy after suffering a wardrobe malfunction while performing on the US version of the celebrity TV show Dancing with the Stars. Despite video evidence to the contrary, she denied exposing her right nipple on prime-time TV.

Even her defenders see Grace as a necessary evil.

"Yes, she panders to the population of people who are so furious about crime that they are willing to cast aside everything to do with due process," says Royal Oakes, a legal analyst for NBC.

"But the American justice system lilts towards being open. Our view is that sunshine is the best disinfectant. The best way to ensure justice is to allow her sort of spirited debate."