The U.S. Congress is examining whether tougher detention policies for illegal immigrants might help prevent serious criminal acts. Lawmakers and immigration experts describe the matter as a longstanding concern, but say it has taken new urgency in the wake of the September 11th terrorist attacks.

Congress has begun a five-year review of the 1996 Illegal Immigration Reform Act. Lawmakers passed that act five years ago, out of concern that too many illegal aliens were being temporarily allowed to live freely the United States, while waiting for their asylum hearings. Many aliens never appeared for their hearings and simply disappeared, while others committed serious crimes.

The 1996 law significantly reduced the number of instances in which authorities could temporarily release illegal aliens while their asylum claims were being processed. Immigration officials say the number of asylum-seekers detained under the law has almost quadrupled, from 5,5000 in 1994, to 19,500 this year.

However, prosecutor Paul Thomson told a congressional hearing Wednesday the scope of the law should be expanded to cover aliens who are in the United States legally, but commit certain offenses.

As an example, Mr. Thomson recalled the prosecution of Eddie Bell, a Jamaican legal immigrant who was waiting for a decision on his deportation case in 1999, two years after he was convicted of carrying a concealed weapon. "On October 30, 1999, Winchester police officer Rick Timbrook was shot in the face at close range by Mr. Bell and killed, as Officer Timbrook tried to arrest him. At the time of the killing, the defendant, Mr. Bell, was on liberty on a $3,500 bond, pending a removal proceeding in the immigration court in Arlington, Virginia," he says. "I believe the facts of this case demonstrate in stark terms the need for immigration detention reform."

Edward McElroy, an official with the Immigration and Naturalization Service, said the 1996 law should be renewed, because illegal immigrants have been involved in terrorist activities in the past. "Paroling such individuals is not in the best interest of the United States," he says. "The negative actions of Ghazi Maizar, the Brooklyn Subway Bomber, or Ramzi Yousef, one of the first World Trade Center bombers, is an indication of what can be expected, should the Service parole those who are found to have credible fear, and who turn out to be less-than-genuine applicants."

Ghazi Maizar, a Palestinian immigrant, was convicted in 1999 of trying to plant a pipe bomb in the New York subway. Two years earlier, Ramzi Yousef was found guilty of helping to plan and execute the first World Trade Center bombing, in 1993.

However, law Professor Margaret Taylor told the committee, an increased number of detentions puts a strain on government resources and is unfair to many immigrants, both legal and illegal. "The INS needs to develop an effective system of reporting and supervision for aliens in proceedings. The majority of criminal suspects are released pending trial. The vast majority of those who are released show up for their trial," says Mrs. Taylor. "By definition, then, most aliens who have been convicted of a crime, and are in the midst of deportation proceedings, have already demonstrated that they will comply with a supervised release program."

Lawmakers insist immigration detention policy was a pressing matter before the September 11 terrorist attacks. They add they now have all the more reason to focus on the topic.