In criminal law, it is undisputed that the best information regarding a crime comes from interviews conducted by law enforcement. Moreover, usually, some of these interviews result in suspect confessions that may be used at the trial against a defendant.
You are the prosecutor in a case in which the defendant has confessed to the crime. However, it is not clear whether the confession was obtained legally. Without the defendant’s confession, you know that you will never be able to get a conviction at the trial.