Negotiated agreements in criminal trials—often, somewhat deprecatingly, called “deals” in Germany—are a curious phenomenon. Such agreements informalize criminal proceedings, yet—according to the legislature—they are also restrained by the formal structure of German procedural law, through the principle of judicial investigation. The restraining of deals via procedural law seems like a futile attempt to achieve the impossible: In an inquisitorial system, the court is obliged to find the “real,” material truth by extending the taking of evidence to all facts and means of proof relevant to the decision. Neither ascertainment of guilt nor sentencing can be based merely on hypothetical facts of the case. A recent judgment of the Federal Constitutional Court on negotiated agreements has stressed that it is unconstitutional to base a conviction on facts that have been mutually agreed upon, if it is not certain that the facts are actually real. This decision hints at the problems deals pose for criminal proceedings in Germany. Despite these problems, such agreements have been very common in the last years and decades. There are many reasons for this. We are going to discuss the most important ones here.