The recommendations, the first from a major police organization to deal with the realities of a post-Sept. 11 world, take a more aggressive posture than typical lethal-force guidelines. The guidelines were published July 8 -- about two weeks before the London police, acting on a similar policy, fatally shot an innocent Brazilian seven times in the head because they mistook him for a suicide bomber.

The National Bomb Squad Commanders Advisory Board is developing the first national protocol for response to suicide bombers and is also recommending to police bomb squads nationwide that if a suspect is wearing a suicide bomb, an officer who needs to use deadly force should not shoot near the bomb.

U.S. police officers and federal agents typically have been authorized to use deadly force if lives are in imminent danger. But since the Sept. 11, 2001, terror attacks, the definition of imminent danger has changed, prompting law enforcement officials to rethink the rules of engagement.

"There is not a responsible chief or head of a law enforcement agency in this country who isn't now pondering the dilemma a suicide bomber presents to their officers," said U.S. Capitol Police Chief Terrance W. Gainer, who became the first chief in the nation to adopt a shoot-to-kill policy if his officers are confronted with a suicide bomber.

After the July 7 attacks on the London transit system by suicide bombers, the international police chiefs organization produced a detailed training guide for dealing with suicide bombers for its 20,000 law enforcement members. It recommends that if an officer needs to use lethal force to stop someone who fits a certain behavioral profile, the officer should "aim for the head" to kill the person instantly and prevent the setting off of a bomb if one is strapped to the person's chest.

The police organization's behavioral profile says such a person might exhibit "multiple anomalies," including wearing a heavy coat or jacket in warm weather or carrying a briefcase, duffle bag or backpack with protrusions or visible wires. The person might display nervousness, an unwillingness to make eye contact or excessive sweating. There might be chemical burns on the clothing or stains on the hands. The person might mumble prayers or be "pacing back and forth in front of a venue."

The police group's guidelines also say the threat to officers does not have to be "imminent," as police training traditionally teaches. Officers do not have to wait until a suspected bomber makes a move, another traditional requirement for police to use deadly force. An officer just needs to have a "reasonable basis" to believe that the suspect can detonate a bomb, the guidelines say.

Last year, Gainer retrained his officers to shoot to kill when faced with a suspected suicide bomber who is uncooperative and refuses to stop and be searched. Other law enforcement officials say they are debating the issue and might follow his lead if there is a suicide bombing in this country.

"I can guarantee you that if we have, God forbid, a suicide bomber in a big city in the United States, 'shoot to kill' will be the inevitable policy," said Miami Police Chief John F. Timoney in an interview. "It's not a policy we choose lightly, but it's the only policy."

In Israel and the United Kingdom, countries with a history of confronting terrorist violence, police have adopted a national policy of shooting a suspected suicide bomber in the head to prevent detonation of a suicide vest. The British order became public last week after the shooting of the Brazilian.

"I really empathize with the British authorities," said Gainer, who is responsible for protecting 535 members of Congress, their staff members and visitors to the U.S. Capitol. "It's a Hobson's choice. How do you control someone you think has a suicide belt on? But what are the consequences of shooting someone, who, because of behavioral profiles, looks and acts like a suicide bomber but turns out isn't?"

Assistant FBI Director Michael A. Mason, who oversees the Washington Field Office, demonstrated the difficulty of the split-second decision with a hypothetical situation: A man in a heavy coat on a hot Washington afternoon heads up the steps of a Smithsonian museum, where a group of children is standing. Someone yells that the man has explosives. Mason identifies himself as an FBI agent and screams for the man to stop, but the man ignores him.

"What do you do?" Mason asked. "I am instantly between a rock and a hard place."

Gainer retrained his officers after a trip to Israel during which he and other chiefs traveled with the Police Executive Research Forum for week-long counterterrorism schooling from Israeli officers familiar with confronting Palestinian suicide bombers.

The Israeli training of British and American law enforcement officials makes some groups ask whether the police are going too far. The tension is especially pronounced among Muslim community leaders, who are deeply suspicious of Israel because of the country's long-standing conflict with the Palestinians.

"The London situation where an innocent man was shot and killed was based on Israeli procedure, and I don't think that we want to be replicating the actions of a foreign government engaged in a brutal occupation of another people," said Ibrahim Hooper, spokesman for the Council on American-Islamic Relations. "It sends the wrong message to the Muslim world."

In contrast to the national shoot-to-kill policies of Israel and Britain, American use-of-force orders are set by each of the nation's 18,000 law enforcement agencies.

A number of high-profile shootings in the past decade, including that of Amadou Diallo, who was shot 41 times in 1999 by New York police officers, highlighted the abuse of lethal force by out-of-control officers and the deadly mistakes that can be made by fearful or reckless police.

Most law enforcement agencies, including the D.C. police, are supposed to use what is known as a continuum of force: If force is used, it should be applied or increased in proportion to the suspect's actions and level of resistance.

Deadly force policies across the country are similar to those of the Metro Transit Police, who patrol the Washington area's subways and bus terminals. "Lethal force can be used if the officer reasonably believes his/her life or the lives of others is in danger or in defense of any person in imminent danger of serious physical injury," reads the Transit Police policy.

With the exception of sniper units or SWAT teams, police officers are generally taught to "shoot to stop" or "shoot to neutralize." Officers traditionally are trained to aim at the center body mass, which offers the largest target, if they are in a situation that requires the use of deadly force.

But now, in the case of a suicide bomber, the international police organization says that tactic would be "inappropriate." According to the group's training guidelines, a bullet could hit an explosive device and detonate it. The bullet also might wound the bomber, who could then detonate an explosive vest. In addition, some explosives -- such as smokeless powder and triacetone triperoxide, or TATP, which apparently was used in the London bombings -- are sensitive to heat, shock and friction, according to the training document.

"You need to get him dead as quick as possible," said Timoney, the Miami police chief. "The easiest way to do that is a head shot. That's the only way to guarantee. It's not something you relish. But if you shot him in the upper torso, that person would be able to make movements and make sure the bomb, if he had it, could go off. A body shot very seldom kills instantly."

David Heyman, director of the homeland security program at the Center for Strategic and International Studies, said he does not think that most U.S. police departments will adopt a shoot-to-kill policy unless there is a suicide bomber on U.S. soil.

But terrorism experts said departments need to move now to develop clear directives and prepare their forces in case that day comes.

"The police standard operating procedure of addressing a suspect and telling them to drop their weapon and put their hands up or freeze is not going to work with a suicide bomber," said Bruce Hoffman, author of "Inside Terrorism" and a terrorist expert at the Rand Corp. "You're signing your own death warrant if you do that."