Final answer:
A conflict of interest in a capital case does not automatically lead to reversal, but if it's proven to affect counsel's performance and was not waived by the defendant, it can result in a reversal based on ineffective assistance of counsel as defined in Glasser v. United States.
Step-by-step explanation:
A conflict of interest in a capital case does not automatically call for a reversal of the case. However, under the Assistance of Counsel Clause of the Sixth Amendment, exemplified in Glasser v. United States, a defense lawyer's conflict of interest due to the simultaneous representation of co-defendants can violate the defendant's right to effective counsel. In such situations, the court must evaluate whether the conflict had an adverse effect on the attorney's performance.
It should be noted that each case involving a conflict of interest is assessed on its own merits. The key factor is whether the conflict had the potential to influence the attorney's performance to the detriment of the defendant. If such influence is established, and the defendant did not waive their right to conflict-free representation, it may lead to a reversal on appeal based on ineffective assistance of counsel.