The Constitution of the United States guarantees that a person accused of a crime is entitled to effective assistance of legal counsel. Furthering that right necessitates a client possessing the ability to convey information to an attorney in complete confidence. An attorney is only able to appropriately represent a client when this level of absolute confidentiality exists.
Clients need to be able to feel comfortable enough with their attorneys to share information with them that they might not otherwise share in order for attorneys to be able to make an adequate case. If this attorney-client privilege was removed from the justice process, it would be unfair to clients who may withhold important information about their case from their attorneys for fear that the information may be subpoenaed. In essence, there is a better chance of complete facts coming out with the attorney-client privilege in place than without it.
In my opinion, attorney-client privilege should not trump justice. It should be reserved for those who have done nothing wrong, but those who would use it for protection from prosecution should not be given it. Those who commit crimes, especially those that are serious or heinous in nature, should realize that they gave up some rights when they chose to commit the crime. Attorney-client privilege should be one of those forfeited rights.
No, the attorney-client privilege should not supersede finding out the facts of a case. Because unless the court discovers everything, no fair verdict can be rendered. Any collusion that is protected by privilege is useless and counterproductive to the goal of the criminal justice system. This attorney-client privilege is not the same as a doctor-patient privilege because nobody has been charged with an offense in doctor-patient relationships. The defendant has rights, but they should not extend to being able to confide with an attorney, whose lips are sealed, about the terrible truth.