The decision to seek the death penalty is one of the most profound responsibilities entrusted to any district attorney. Seeking a punishment that ends the life of a human being, even when that person is accused of having committed murder, is a solemn and sobering decision that cannot be taken lightly.

In the Los Angeles District Attorney's Office, when I led it, the decision to seek a death-penalty sentence was the result of an intensive process, but the final decision was mine alone.

In an upcoming U.S. Supreme Court case, Williams v. Pennsylvania, a former district attorney argues that his decision to seek capital punishment was an administrative act that did not bias his later adjudication of the case while on the state Supreme Court. My experience suggests otherwise.

Williams v. Pennsylvania will be heard on Monday, in one of the first cases to be argued without the presence of Justice Antonin Scalia. The case addresses the refusal of Ronald Castille, the former chief justice of the Pennsylvania Supreme Court, to recuse himself from appellate review of the case of Terrance Williams, a death-row prisoner.

Before he was elected to the state Supreme Court, Castille was the district attorney of Philadelphia, and in that capacity he sought a death sentence against Williams, which he authorized in a handwritten note. Castille led the city's District Attorney's Office during the trial, capital sentencing, post-trial, and direct appeal proceedings in Williams' case. When he ran for election to the state Supreme Court, The Inquirer reported that Castille proclaimed that he "sent 45 people to death row." Among them was Williams.

However, in 2012, a state court found that the District Attorney's Office under Castille's leadership committed prosecutorial misconduct in Williams' case, illegally withholding important mitigating evidence from Williams' defense lawyer. A new sentencing hearing was ordered.

When the current district attorney of Philadelphia appealed the decision, it went to the state Supreme Court, where Castille had become chief justice. Williams' attorneys requested that the chief justice recuse himself, or put the question of his recusal to the full court. Castille refused to do either and remained on the bench in consideration of the case, despite the fact that it involved an accusation of misconduct against his former office and the reversal of a death sentence he personally authorized as district attorney.

Many former prosecutors, former judges, legal ethicists, and others share my concern about this case.

The Commonwealth of Pennsylvania and Castille argue that the decision to seek the death penalty against Williams was purely ministerial, that Castille had no knowledge of the facts of the case, and that therefore he could review the death sentence with no preconceived feelings or opinions about the case.

Pennsylvania and Castille also argue that Castille's supervisory role over the prosecutor who committed misconduct in Williams' case did not affect his ability to be fair when judging the case. My experiences as the Los Angeles County district attorney for eight years and as chief deputy district attorney for four years make it clear to me that these arguments hold no water.

I believe that it would be difficult, if not impossible, for Castille to fairly review the lower court's decision that a prosecutor he supervised committed misconduct. A district attorney is responsible for the professional conduct of his or her deputies. Misconduct of one deputy reflects on the integrity of the office as a whole, and accusations of misconduct implicate problems with leadership.

The lower court's finding in Williams' case that a deputy committed misconduct indicated failings in Castille's leadership that I do not believe he would be able to review and consider impartially.

A judge must always "hold the balance" in our legal system in order for the public to retain its confidence and trust in the courts. The U.S. Supreme Court should send Williams' case back for consideration by a court that does not include Castille.

Gil Garcetti served 32 years in the Los Angeles District Attorney's Office, including 12 years as the district attorney and as chief deputy.