It is a practice where investigators single out individuals for investigation on the basis of race, national origin or ethnicity.
For years African-Americans have claimed they have been unfairly targeted, particularly for traffic stops, because of their race. It gave rise to the derisive term for such stops: "DWB" - driving while black.
Many police forces for years denied the practice even occurred before "discovering" documents that proved the practice - often after newspaper or internal investigations. The Drug Enforcement Agency's "Operation Pipeline" during the 1980s targeted blacks on New Jersey highways and its guidelines cited that "blacks value material goods, blacks who are not able to purchase their own home put money into cars".
Over the past few years, many states have restricted the practice and, on a federal level, bills have been introduced in the Senate and the House to ban profiling.
And then came the September 11 hijackings.
With all 19 suspects being of Arab origin, racial profiling became overnight a natural and acceptable tool of law enforcement.
"We have to be careful we don't let political correctness take us over to the point where we overlook the fact that all the hijackers were Middle Eastern and spoke Arabic to each other," said Floyd Abrams, a noted constitutional lawyer who cautioned against racial profiling in a 1997 report to Congress.
Even the African-American community has backed the practice this time. According to a recent Gallup Poll, blacks are more likely than all other racial groups to favour racial profiling and tougher airport security checks for Arabs and Arab-Americans.
Though the FBI denies bias in its investigation, many in the US Arab and Muslim communities are unconvinced. Dr Riad Abdelkarim, a California physician questioned by the FBI five days after the attacks, said the experience reminded him of a "B" movie. The agents knocked on his front door dressed in dark suits, ties and sunglasses. They seemed to know little about him or his views despite the fact that he regularly writes opinion pieces for newspapers throughout the US. Their questions were directed at determining if he was a terrorist sympathiser.
"They asked me: 'Are we the bad guys in this thing?"'
Manal Kreshi and her husband Hani Teebi were also questioned by the FBI last week. Both are Kuwaitis who emigrated to the US in the 1980s. Manal was too afraid to leave her house for a week after the attacks and has still not returned to the mall because of reports of widespread assaults and abuse against those who look Arabic. A friend - a dark-skinned Hispanic woman - was shot at and nearly killed by someone in a passing car.
The couple say the FBI sought them out because of an anonymous tip. Among the tips the agency is reported to have followed up on are homes where the blinds were consistently shut and residents who did not socialise with neighbours.
Many in law enforcement criticise the use of profiling because it is inefficient and promotes tunnel vision.
Authorities can become so focused on people fitting pre-determined characteristics that they miss suspects who stray from the mould.
In 1998, the US Customs Service eliminated racial and gender profiling. "What we told people is that broad racial profiling doesn't make sense," says former Customs commissioner Raymond Kelly.
Under Kelly, the bureau began a passenger analysis system which checked travel itineraries and embarkation points.
With the new system, customs made 70 per cent fewer searches and increased its yield of illegal substances by 25 per cent.
For now there is little doubt that anger and prejudice have fuelled at least some of the stops.
"If I see someone comes in that's got a diaper on his head and a fan belt wrapped around it," said Louisiana Congressman John Cooksey, "that guy needs to be pulled over and checked."
There is evidence that the anti-Arab hysteria is ebbing.
But still, even liberal commentators concede times have changed dramatically for law enforcement.
Racial profiling, only recently relegated to the scrapheap of police practices, is back with a vengeance.
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