The practice of stopping people at Boston's Logan Airport and detaining them for questioning based on their behavior is unconstitutional and must be stopped, the American Civil Liberties Union has said in a lawsuit.

The group challenged a program known as "behavioral pattern recognition," which Massachusetts state troopers have used at Logan Airport since 2002 and which is serving as a model for a similar program to be launched at airports across the country.

The ACLU said current law allows police to stop people when they have a reasonable suspicion that the person may commit a crime or has already committed one.

The behavioral profiling program, however, instructs officers to detain anyone they believe is exhibiting "unusual" or "anxious" behavior, the ACLU said.

"This program is another unfortunate example of the extent to which we are being asked to surrender basic freedoms in the name of security," John Reinstein, legal director of the ACLU of Massachusetts, said in a statement.

The group filed the suit on behalf of King Downing, national coordinator of the ACLU's Campaign Against Racial Profiling.

According to the lawsuit, Downing was approached by law enforcement officials after he arrived at Logan more than a year ago to attend a meeting on racial profiling.

A state trooper stopped Downing, a black man with a short beard, and asked to see identification. When Downing refused to show identification without first knowing why he was being stopped, he was told he would have to leave the airport.

But when Downing tried to go, the trooper followed him and again demanded identification. Downing was then surrounded by three other troopers and told that he was being placed under arrest for failing to show identification.

He finally agreed to show his identification and travel documents and was allowed to leave. No charges were filed.

"This is a dangerous extension of police power," Downing said in a statement. "This is racial profiling, and not the action of a government that stands for freedom and the rights of all its people."

The lawsuit was filed in Suffolk Superior Court.

The Massachusetts State Police said in a statement a lack of cooperation by the ACLU had hindered its investigation of the incident and it looked forward to "bringing all the facts of the case to light."

A spokeswoman for the agency that runs Logan airport did not return a call seeking comment.

(Reuters)