Police processing crime scenes now over-collect evidence, and prosecutors order unnecessary tests to make sure that every eventuality is covered, Mr. Houck said. Defense attorneys, too, get in on the act, he continued, by demanding perfect science all the time.and
... Mr. Houck cited jurors who have said they found defendants "not guilty" because there was not enough physical evidence presented, even if there was overwhelming circumstantial evidence.and
I encourage you to read the entire article, which only runs about a page but its every word is "spot on", as the British say. My compliments to Paula Ward of the Pittsburgh Gazette for her reporting from the perspective of real-world forensic science.
... make the public believe that the scientists' resources are unending, Mr. Houck said. The labs on television have unlimited budgets and access to the best equipment in the world -- something that is uncommon in the real world.
According to a study by the U.S. Department of Justice at the end of 2002, there was a backlog of more than half-a-million cases in crime labs across the country.