She is best known as one of the legal defenders of former Iraqi president Saddam Hussein when he was on trial for genocide and crimes against humanity. Khalil joined Hussein's legal team just days after his capture in 2003; her participation attracted controversy because Khalil is a Shi'ite Muslim. She believed her status as a Shi'ite would render the prosecution of Hussein more difficult. Khalil is reported to be the only woman that met Hussein during the months of his trial. Khalil was repeatedly thrown out of court during Saddam's trials, after disruptive behavior and arguments with the judge. Khalil also represented other defendants associated with the Hussein regime, including former Vice President of IraqTaha Yassin Ramadan. Her public role as a legal representative of the former regime caused her to face repeated death threats.
In previous years Khalil had campaigned repeatedly for a seat in the Lebanese Parliament, but was never elected.