Defense attorneys know how to use constitutional guarantees that are advantageous to their clients. For example, all criminal prosecutions are based upon evidence gathered. This may include physical items of evidence, witness statements, confessions, drug and alcohol tests, and so forth. The Forth Amendment to the U.S. Constitution (applicable to the states through the 14th Amendment) prohibits the police from using unreasonable searches and seizures to gather evidence. If they do, a good defense attorney will ask the court to suppress that evidence so it cannot be used at trial.