[JURIST] US Supreme Court nominee Samuel Alito [White House profile; US News profile] said Thursday that during his 15 years as a federal court judge, he never knowingly ruled on a case in which he had an obligation to recuse himself. Alito was responding to challenges made by US Senate Democrats Wednesday that Alito heard a 2002 case involving mutual fund company Vanguard [corporate website] when he had a six-figure investment with them, despite making a promise in 1990 to disqualify himself from cases involving certain firms, including Vanguard. Senate Judiciary Committee [official website] Chairman Arlen Specter (R-PA) [official website] sent Alito a letter Thursday urging him to promptly explain why he ruled in cases involving Vanguard and Smith Barney [corporate website], another firm that helped manage Alito's investments. Alito responded, "I have been committed to carrying out my duties... in accordance with both the letter and spirit of all applicable rules of ethics and canons of conduct," adding that he had concluded "there was not a legal or ethical obligation under the applicable rules... to recuse myself from every case involving the companies I listed." The White House has denied any wrongdoing by Alito. Reuters has more.