In 1997, a Sudanese man named Jamal Ahmed al-Fadl became the first person to plead guilty in the United States to offenses related to being part of al Qaeda. Between al-Fadl’s conviction and the end of 2011, 170 other individuals have been convicted by American courts or military commissions for committing crimes on behalf of, or inspired by, the organization responsible for the 9-11 attacks.

A new study finds that a majority of these operatives were American citizens. Nearly a quarter were converts to Islam. More than half had completed some form of college course work.

Some of the names are well known, such as John Walker Lindh, the American who was found by U.S. troops in 2001 to be fighting with the Taliban in Afghanistan. Others are described as al Qaeda aspirants, and were arrested and convicted of plotting terrorist acts after an informant or undercover FBI officer lured them into a sting.

While several organizations have examined the trend of Americans joining al Qaeda, the new study from the Henry Jackson Society, a right-leaning think tank in London, goes into specific biographical and demographic detail on the individuals themselves.

The study is especially timely this month as the Senate Select Committee on Intelligence has demanded President Obama release Justice Department legal memos spelling out his authority to kill U.S. citizens who have joined al Qaeda overseas. Senator Rand Paul, a Republican from Kentucky, has threatened to hold the nomination of John Brennan to be the next CIA director until he gets a statement from the White House that Obama does not have the authority to use drones against American citizens on American soil.

As for who joins al Qaeda, the report says there aren’t many advance signs. “There needs to be an acknowledgement that the threat can come from any region of the country, from any background or educational status,” said the report’s main author, Robin Simcox. “There is no classic profile for the home grown al Qaeda threat in the United States, the key here is to look at the spread of ideology and not profile for education, race or social status.”

Mike Hayden, the last CIA director under George W. Bush and the author of a preface to the new study, compared it to a baseball encyclopedia. “The way I would view this, this is not about targeting Americans or American groups, this is about being aware that Americans and American groups are being targeted by al Qaeda for recruitment,” he said.

This is a very different picture of the al Qaeda threat top national security officials warned about after 9-11. In that world, the threat was largely from highly trained individuals who infiltrated into the U.S. on fake passports or through other means. The report found that only 47 percent of the individuals convicted of al Qaeda-related offenses attended some kind of training camp. Of those who received training, 68 percent attended a camp in Afghanistan, 29 percent in Pakistan and 5 percent in Somalia.

Of the 171 convicted, 61 were born in the U.S. Of those, 17 are African American and 13 are Caucasian. The rest include Iraqi-, Jordanian-, and Egyptian-Americans.

The study also shows that 89 of 171 individuals convicted have received at least some kind of college education, with 39 individuals earning an advanced degree. At the time of their arrests, 97 of the total either had jobs or were in school.

Al Qaeda-related offenses, as defined by the study, can include anything from providing material support to al Qaeda to participating in attempted mass murder. The vast majority of the data for the report is culled from documents from U.S. federal court cases.

“As shown by many years of real-world experience, our federal courts are fully capable of handling terrorism prosecutions,” said James Benjamin, a lawyer with Akin Gump who authored a report in July 2009 on U.S. prosecutions of terrorism cases for Human Rights First. “Compiling statistics requires judgment calls, but we can all learn a great deal from the extensive factual record of successful terrorism cases in our courts during the past 15 years.”