During five days as the star witness in a federal terrorism trial in Chicago, David Coleman Headley revealed details of what he described as his links to both Pakistan’s intelligence service — the ISI — and the terrorist organization Lashkar-i-Taiba. He also presented a portrait of himself as a man whose double life depended on lying and manipulating his wives, colleagues and closest friends.

The trial provided the first public view of Headley, a Pakistani-American who was once a DEA informant, since his arrest and confession to having played a key role in a 2008 terror attack in Mumbai. Speaking in a low, scratchy voice tinged with just the slightest Pakistani accent, Headley testified against his childhood friend Tahawwur Rana, charged with supporting Headley’s involvement in terror plots in Mumbai and Copenhagen.

In testimony in Chicago, Headley said that at the time the Mumbai attack, which killed 166 people, gave him the satisfaction of revenge for Pakistani deaths in the decades-long conflict with India. But almost three years later he professed a remorse about the civilian deaths. “I have regrets,” he said. “I have had time to reflect.”

FRONTLINE and ProPublica have spent six months so far investigating Headley’s connections to terrorism, and ProPublica’s Sebastian Rotella has been reporting from the courtroom.

One of the top Pakistani militants linked to Al Qaeda and an alleged contact of Headley’s, Ilyas Kashmiri, was reported killed last week in an American drone strike. But U.S. and Pakistani officials were reportedly awaiting confirmation of his death.

Headley’s public appearance has been long awaited, especially by observers in India and Denmark, sites of his plots. The defense in the case played brief segments of his videotaped interrogation with FBI agents, showing Headley eager to talk about what he knew — perhaps because, after striking a deal to save him from the death penalty, his life literally depended on it. Rotella describes the scene in court:

Tom Jennings is producing a documentary on David Coleman Headley scheduled to air on FRONTLINE on Nov, 22, 2011.

Tom Jennings