Television has had a negative impact on the image of the judicial system. It seems that all crime dramas on the television today have the infamous DNA evidence in hand to properly convict the bad guy.
Although DNA testing has come light years since its initial launching, it is still something you don't get every day. DNA testing takes time and money, money that isn't spent unless absolutely necessary.
DNA tests are generally run in higher felony cases. Murder, rape and terrorist cases are apt to bring in DNA evidence, if need be. In the case of some teenager holding up a local drugstore it is probably not going to involve DNA or fingerprint analysis.
The fact is, if you have jury duty, don't expect to have to wade through fancy DNA fact or listen to fingerprint experts, that is television. Although it is sometimes needed in the courtroom, it is not the norm.