Who are the suicide bombers? Pakistan's answer.

In four years, 28-year-old Gul Hasan went from laying bricks to recruiting suicide bombers. An antiterrorism court convicted Mr. Hasan this month of planning suicide attacks on Shiite mosques in Karachi that killed dozens of worshipers. Now he faces the gallows.

How people like Hasan get involved with militant Islam, and what they do to recruit others, are questions of increasing urgency in Pakistan, which has seen a spate of suicide bombings in recent weeks.

The attacks were carried out by splinter groups formed in the wake of a Pakistani crackdown on militant Islamic organizations after Sept. 11, 2001. Smaller and more isolated than their parent organizations, these splinter groups receive financial backing from Al Qaeda and draw their recruits from the ranks of the poor and enraged, say Pakistani investigators.

"This is a new breed [of militants], as suicide bombings are a post 9/11 phenomenon here," says Fateh Mohammad Burfat, head of the Criminology Department at the University of Karachi. The bombers are "unemployed, illiterate, and belong to poor social strata. [They also] perceive the US military actions in Iraq and Afghanistan as hostile acts against the Muslim world.... By suicide attacks, they get a sense of victory in the world and hereafter."

Hasan entered the world of militant Islam when his brother, a member of the splinter group Lashkar-e Jhangvi, was arrested. Over time, Hasan went from being a simple carrier of weapons to a dangerous militant leader in Karachi responsible for recruiting and transporting suicide bombers, say police officials.

The splinter groups "provide the new entrants with poisonous extremist literature to brainwash them, and then start giving them responsibilities from shifting weapons to providing refuge to wanted militants," says Gul Hameed Samoo, a Karachi police official. "One rises through the ranks after fulfilling [certain] tasks."

The leaders recruit them for different purposes, with agendas ranging from killing Shiites to liberating Muslims from "infidels." The new trend of suicide bombings is packaged as a "ticket to Paradise."

Many of the splinter groups' top leadership fought in Afghanistan and Kashmir. They are believed to have made contacts and trained with Arab militants in Afghanistan.

Police investigators describe three layers of organization behind suicide attacks. In most of the cases, the mastermind is Al Qaeda, which gets in touch through a courier with the leader of a jihadi splinter group who plans the attack. The attacker is often a "brainwashed" jihadi.

In the case of the unsuccessful suicide attack against Pakistani President Pervez Musharraf on Christmas Day 2003, police say the mastermind was Abu Faraj, an Al Qaeda operative now in custody; the planner was Amjad Farooqi; the slain chief of Lashkar-e Jhangvi; and the bomber was a local jihadi.

In a New York Times opinion piece on Tuesday, Peter Bergen, author of "Holy War, Inc.," and Swati Pandey argued that the Islamic terrorists behind many of the attacks against the West are well-educated - not brainwashed youth from madrassahs, or Islamic schools. In a sampling of 75 terrorists involved in attacks against Westerners, they found that 53 percent had attended college - a figure slightly higher than US averages. "[Madrassahs] are not and should not be considered a threat to the United States," the authors wrote.

In Pakistan, where many of the suicide attacks do not directly target Westerners, the Al Qaeda masterminds are often well- educated, but the planners and the bombers themselves generally are not.

"There are leaders who look out for suicide bombers and usually find the simple, unemployed religious-minded youth with the help of a cleric at a mosque or madrassah," says a police investigator.

Hasan, the recruiter of suicide bombers, has an eighth-grade education. Mohammad Jamil, one of the two suicide bombers behind the Christmas attack on Mr. Musharraf, was a dropout who studied at a madrassah in Pakistan's Frontier Province. Neither Mohammad Ali Khatri nor Akbar Niazi, two suicide bombers who killed 40 worshipers at two Shiite mosques last year, completed high school.

Recent interrogations have shed light on how bombers are recruited and groomed. A police investigator quoted a detained sectarian militant, identified as Tehseen, as saying, "We isolate the boy who is willing to sacrifice his life. From then onwards he does not have any contact with his family or friends. We provide him religious books, and he prays all the time before [his] mission."

Police nabbed Tehseen after he was injured at the scene of an attack on a Shiite mosque in Karachi this month. He was accompanying the suicide bomber as a guard.

"In some cases, the suicide bomber gets terrified after reaching the target and flees. [The leaders] sometimes take the family hostage if the suicide bomber changes his mind," the police investigator says.

The suicide-bomber cells operate in small groups of five to seven people, never staying at one place for more than two nights, says a police investigator.

Moving in small cells is now a necessity for members of the larger splinter groups, which have been thrown into disarray by a persistent government crackdown, officials say. They add that the isolation of splinter groups, as well as their greater dependence on outside funding, may explain the adoption of the radical tactic of suicide bombing.

"They are on the run, and short of resources. But it is the most dangerous tactic and rather impossible to stop like elsewhere in the world," says Karachi police chief Tariq Jameel. "We have to create awareness and counter them by eliminating extremism from the society, which is the best antidote to terrorism. Otherwise suicide bombings can give these disarrayed splinter groups a new life."

Last month, a group of 58 religious scholars issued a fatwa, or religious edict, saying that Islam strictly forbids suicide attacks on Muslims. Further, those committing such acts at public congregations or places of worship cease to be Muslims.

"Killing of any non-Muslim citizen or foreigner visiting the country is also forbidden in Islam since they are under protection of government of Pakistan," said Mufti Munib-ur Rehman, one of those issuing the edict.