When Daveed Gartenstein-Ross worked at the U.S. headquarters of Al Haramain Islamic Foundation in 1999, his boss used to joke that prison inmates studying Islam were "a captive audience," he testified Tuesday before the Senate Committee on Homeland Security and Governmental Affairs.

The Treasury Department has since designated Al Haramain as a sponsor of terrorism with ties to al-Qaida. The boss and group's director were indicted for money laundering.

Gartenstein-Ross had left the group and Islam before Sept. 11, 2001. When the FBI began looking at Al Haramain, he was happy to cooperate. On Tuesday, he spoke before the Senate committee to address a scary front in the war on terror -- would-be warriors who already are behind bars.

Next August, what may prove to be the most chilling example -- California State Prison-Sacramento inmate Kevin James -- will go to trial with three co-conspirators. Last year, the feds indicted James on charges that he masterminded a plot to kill U.S. military personnel, Israeli officials, and people at recruitment centers, synagogues and El Al airline facilities.

According to reports, when a James' devotee was paroled, he recruited two men from a mosque. They began robbing gas stations to fund their attacks. One carelessly left a cell phone at a robbery site. Local law enforcement following that lead saw a list of targets and alerted the feds. All the while, James was in prison -- where officials knew nothing about the plot, Gartenstein-Ross told me.

Prisons always have been breeding grounds for extremism, gangs and violence, according to a George Washington University report highlighted at the Senate hearing, "Out of the Shadows: Getting Ahead of Prisoner Radicalization."

Think Aryan Brotherhood. It's not a long jump to Richard Reid, who converted to Islam in a British prison, then tried to blow up a plane with a shoe bomb. Continued...