Editor's note: This story includes a correction.
ISLAMABAD, Pakistan -- A prominent American lobbyist is at the center of the criminal case alleging ex-Pakistani dictator Pervez Musharraf played a role in the assassination of former Prime Minister Benazir Bhutto.
Mark Siegel, a Washington, D.C.-based former adviser to Bhutto, submitted testimony to the court which appears in an investigative report prepared by the Federal Investigation Agency, Pakistan's version of the FBI.
Siegel shared details of an exchange between himself and Bhutto after she finished a phone conversation with then-President Musharraf in September 2007. He claims she seemed "shaken" after the call, and said Musharraf "did not want her to come back to Pakistan," saying "her safety depended on the state of her relationship with him."
At the time, Bhutto was preparing to return from exile to lead her Pakistan People's Party in upcoming elections. The federal government, led at the time by Musharraf, was responsible for providing her security in Pakistan.
Details of Siegel's alleged exchange with Bhutto were published by the New York Daily News in 2012 as well as the claim that Bhutto emailed him after a failed suicide bomb attack against her soon after returning to Pakistan, saying that "if anything happened to her, she would hold Musharraf responsible." Bhutto was killed in a gun and bomb attack at a political rally in Rawalpindi two months later.
Siegel is described as a "lifelong friend" of Bhutto on his law firm's website.
The bio adds: "Siegel has three times represented Pakistani governments in Washington, D.C. He was Ms. Bhutto’s speechwriter for two decades, and collaborated with her on the international bestselling book 'Reconciliation: Islam, Democracy and the West' which was published shortly after her assassination."
Siegel was producer of "Bhutto," a feature-length documentary which appeared at the 2010 Sundance Film Festival.
Now a partner at Locke Lord Strategies, he has taught at the American University, Loyola University and George Washington University and currently lectures at Columbia University, according to the site.
Siegel also worked as a lobbyist for 25 years and is a former executive director of the Democratic National Committee. He served as deputy assistant to President Jimmy Carter.
A representative for Siegel said he'd been advised by legal counsel not to comment further on the case at the moment.
Musharraf's legal team claims the indictment is "solely based" on Siegel's testimony and called the charges "politically motivated."
Musharraf, who seized power in a 1999 coup, pleaded not guilty to all of the charges.
The general-politician Musharraf has seen his star rise and fall over the past decade as international leaders have struggled to figure out just what to do with one of the keystone countries in the fight against Islamic extremism.
Musharraf enjoyed something of a cozy relationship with President George W. Bush’s White House in the years after 9/11 as the administration looked for allies in the war on terrorism, with the president calling the leader a “strong defender of freedom and the people of Pakistan” during a visit to Washington, D.C., in September of 2006. Those ties proved problematic for Bush only a year later, when Musharraf imposed emergency rule and suspended the constitution.
The Pakistani leader has also has shown a certain savvy for PR in the world of new media. A Facebook page for the former president of Pakistan has one million likes, and he has made two appearances on America’s premier faux news program, The Daily Show with Jon Stewart, to trade barbs with the comedian. Musharraf plugged his memoir “In the Line of Fire” when he appeared on the program in September of 2006, when he was still president.
Five years later, and shortly after Osama bin Laden was killed by Navy SEALs at his compound in Abbottabad, he took sips of orange Gatorade on Stewart’s show while fielding questions about how his country’s military and intelligence services had missed the terrorist mastermind who was hiding right under their collective nose.
The prosecution will begin to present evidence later this month; a lawyer for Musharraf said the former president will not appear, as he's been granted an exemption due to security concerns.
Tuesday's charges mark the first time a former military leader has faced criminal proceedings in Pakistan, where the powerful army has ruled the country for nearly half of the nation's history.
NBC News' Matthew DeLuca and The Associated Press contributed to this report.