Research indicates that mandatory minimum sentencing effectively shifts discretion from judges to the prosecutors. Prosecutors decide what charges to bring against a defendant, and they can "stack the deck", which involves over-charging a defendant in order to get them to plead guilty. Since prosecutors are part of the executive branch, and the judicial branch has almost no role in the sentencing, the checks and balances of the democratic system are removed, thus diluting the notion of separation of powers. Opponents of mandatory sentencing argue that it is the proper role of a judge, not a prosecutor, to apply discretion given the particular facts of a case (e.g., whether a drug defendant was a kingpin or low-level participant, or whether sex offender registration is an appropriate measure for a given crime and offender). When prosecutors apply discretion, they tend to invoke sentencing disparities when choosing among a variety of statutes with different sentencing consequences. In addition to fairness arguments, some opponents believe that treatment is more cost-effective than long sentences. They also cite a survey indicating that the public now prefers judicial discretion to mandatory minimums.