Badat is now serving a 13-year sentence in a British prison. He told prosecutors that he decided to “get away from danger and introduce some calm in his life.”

Badat’s case sheds some light on a rarely considered question: Why do some terrorists drop out? We rightly think of al-Qaida and other jihadist groups as formidable foes, but the stories of would-be killers who bail give us some intriguing clues about fault lines that counter-terrorism officials should exploit.

It’s become a truism of counter-terrorism that we must understand how and why individuals become jihadists in the first place. But almost nobody is studying the flip side of radicalisation — understanding those who leave terrorist organisations. Understanding the dropouts should make it easier for governments to determine which terrorists might be induced to switch sides and help stop radicalisation. The more we know about why terrorists bail, the better we can fight them.

So where to start? Despite al-Qaida’s reputation for ferocity, plenty of wannabes wind up dropping out from it and its affiliates. Consider the September 11, 2001, plot. Even in Osama bin Laden’s greatest triumph, not all of his recruiting efforts paid off. Two Saudis who were selected, Mushabib al-Hamlan and Saud al-Rashid, decided not to participate in the attacks after leaving the training camps in Afghanistan. And in the summer of 2001, Ziad Samir Jarrah, who became the hijacker pilot on United 93, agonised about whether to withdraw from the operation.

Key members have turned against the al-Qaida from its earliest days. These include Jamal Ahmed al-Fadl, a Sudanese radical who was one of the group’s first members and helped work (unsuccessfully) in the early 1990s to procure uranium for the organisation; Essam al-Ridi, an Egyptian veteran of the 1980s jihad against the Soviets who later purchased an airplane in the United States to help ship Stinger missiles from Pakistan to Sudan; and L’Houssaine Kherchtou, a Moroccan who trained to serve as bin Laden’s personal pilot. All three became prosecution witnesses in the trial of the bombing of the US embassies in Kenya and Tanzania in August 1998.

Looking at al-Qaida dropouts, some clear patterns emerge. Some left after becoming disillusioned with the group’s tactics and strategy. Probably the unkindest cut from any former member was delivered by bin Laden’s fourth son, Omar bin Laden, who had spent nearly five years living in Afghan training camps. After 9/11, Omar quit al-Qaida, calling the attacks “craziness”, according to the journalist Peter Bergen. “Those guys are dummies,” bin Laden’s son said. “They have destroyed everything, and for nothing. What did we get from September 11?”

Another factor driving jihadists to drop out is a general lack of respect for the group’s leadership. Ridi testified during the embassy bombings trial that he resented having to take battlefield orders during the Afghan jihad from bin Laden and others who lacked military experience. For Ridi, the final straw was a battle in which many jihadists died thanks to inept leadership, but that al-Qaida nonetheless declared a victory. Jarrah, the 9/11 pilot, felt cut out by ringleader Mohamed Atta’s leadership style.

Another reason bad guys bail out is money. Like the rest of us, some terrorists see inadequate compensation as a sign of unfair treatment. Fadl, the Sudanese radical, fumed over his salary while al-Qaida was based in Sudan and began embezzling funds — stealing approximately $100,000 from bin Laden. When bin Laden got wind of Fadl’s theft, he ordered Fadl to repay the money; after forking over about $30,000, Fadl fled, fearing retribution.

The final factor seems to be good old family ties. Terrorists who maintain contact with friends and family outside their cell or organisation seem more likely to drop out.

There’s no obvious silver bullet here, of course. But the tales of the terrorists who weren’t are of more than academic interest. We’d do well to spend some time trying to understand how Mr. Hyde turns back into Dr. Jekyll.

Jacobson, a former staff member of the 9/11 commission, is a senior fellow at the Washington Institute for Near East Policy.