You do not have to been convicted to give a DNA sample. You could be ordered to give a sample prior to even going to court. Some states have proposed setting up DNA banks of all citizens for identification purposes. I have not heard if this is legal or not. The last few years almost all police agencies take hair samples with the finger prints and mug shots of anyone arrested. If you are a suspect in a crime where DNA could be used against you, be prepared give a sample.