Yeah, all the lawyers and judges I've talked to hate CSI (the show) for what it has done to people's expectations. The legal system does not operate like it is portrayed on TV. It really does come down to "what story is more believable?"

Sometimes a story is more believable because there is incontrovertible physical evidence. Normally in those circumstances it'd never go to the court room though -- plea deal in criminal cases, settlement in civil.