Why do we file a motion to suppress? What is the purpose? How does it help my case?
If you win a motion to suppress, the evidence you seek to suppress is not admitted against you in your trial. If you seek to suppress cocaine and the motion is granted, the cocaine is not admissible against you at your trial. If the cocaine is the only illegal item seized from you and it is suppressed, the district attorney has no evidence and your case will be dismissed. In many drug cases, the motion to suppress the narcotics is the only defense in the case.
Drug crimes lawyers refer to the law of suppression in drug and narcotics cases as the Exclusionary Rule. The basis of a motion to suppress is under the fourth amendment of the United States Constitution and Article I Section VIII of the Pennsylvania Constitution. When the motion is granted, the evidence is excluded, hence exclusionary rule.
Foundationally, Wong Sun v, United States, 371 U.S. 471 (1963), created the legal reasoning behind the exclusionary rule, enabling the practice of excluding from evidence, that which was seized illegally, enforcing our rights to be free from illegal search and seizure. Without the exclusionary rule, the judge could rule the narcotics were seized illegally and you were searched illegally, but what would be your remedy? Wong Sun laid out the framework for the current day motion to suppress.
In addition, the theory behind suppression is often called fruit of the poisonous tree. Fruit is the illegal item seized by the government and the poisonous tree is the illegal conduct of government. For example, the police illegally stop a car and illegally question a suspect. As a result of the illegal stop and questioning, the police seize a kilogram of cocaine from the car. The poisonous tree is the illegal activity of the police: the stop and questioning. The fruit is the kilogram of cocaine. Accordingly, the cocaine should be suppressed, making it inadmissible at trial.