When I watch movies about a case I always here the saying..."I plead the fifth." When you plead the fifth, you are exercising your fifth amendment right to not incriminate yourself with testimony. The fifth amendment says you have the right to not testify and incriminate yourself. But if you decide to plead the fifth, you probably have to plead everytime and if you do answer the question then you lost your right. By saying you plead the fifth doesn't mean that you still can't be found guilty.
This video demonstates the fifth amendment and he explains how he approaches an individual that is involved with something. He goes through the rights with them and lets the individual know that they do have the right to remain silent. If you lie and the police go to the judge, then that can hurt them more than if the individual would have just talked to the police and be honest. If you talk to the police everything will be written down, and if you get pulled over the cop writes everything that is said.