The Fourth Amendment was created to protect you from an unlawful search. In many cases, this means that the police cannot come into your home without a warrant. You have a right to privacy. This is occasionally overruled in specific situations -- like if they see you commit a crime in your driveway and then run into your house -- but warrants are typically needed.

Electronic Protections

The Fourth has also been interpreted to apply to electronic communications. If the police want to read your text messages, read your email, or tap your phone, they have to get a warrant first. Looking at your communications is a "search" because the police are searching for information, the same way they would be if they came into your home.

Poisonous Fruit

Because of these protections, a doctrine known as the "fruit of the poisonous tree" has been established in U.S. law. Essentially, the "fruit" is any evidence that is found as a result of an illegal search. This evidence cannot be used in court.

It may not always be gathered immediately. For example, if the police illegally tap your phone and hear you say that you have illegal drugs in your home, and then they go into your house and find them, the drugs they discovered can't be used as evidence. Even though they had probable cause to search your house, they obtained that cause illegally, so everything that is directly discovered because of the illegal wire tap can't be used. This can extend outward to a lot of evidence.

Protecting Yourself

Knowing how this works is critical in criminal cases. Even if you're accused of a crime, you still have rights as a U.S. citizen, and they have to be respected. The country is entirely based around this idea of individual rights. If yours were violated, you may be able to have incriminating evidence removed from court, which could end the case if that's all of the evidence the police have.