What is the role of the Exclusionary Rule in the court?
In addition to preventing police and prosecutors from using blatantly illegal tactics to gather evidence and statements, the Exclusionary Rule forces them to follow the letter of the law regarding the limits of police power, and the legality of investigative techniques.
For example, a search warrant is a very specific document, with a date, time range, address and item list for the search. It may say the "living areas" of the home only, which means the garage would be excluded, and the outbuildings too. The Exclusionary Rule forces the police to follow the judges order to the letter, because if they do not, then the evidence won't be used anyway. It is a very effective means of controlling the actions of the police in the field (and one of the few effective techniques).
While I am sure it is frustrating for police, who have a tough job already, it does protect us from expanded or abused police power, and society has decided early on that using the Exclusionary Rule, and allowing some criminals to go free on occasion is acceptable if it is needed to protect the legal and privacy rights of all citizens from abuse of power by the government.
Below are links to two articles debating this issue.
The role of the exclusionary rule is to prevent police from using illegal tactics to obtain confessions or evidence for use in a trial. This rule has been controversial because conservatives, especially, feel that it excessively hampers police actions.
If police obtain a confession outside the rules, or if they search a home without a warrant, for example, what recourse does a defendant have? Right now, the recourse is the exclusionary rule -- the illegally obtained evidence cannot be used in court. Opponents of the rule say that the rule serves only to help people who are guilty to evade punishment.