Polly Klaas was murdered by her abductor shortly after he was pulled over for a routine traffic stop. Although the police encountered Klaas's abductor and killer in the area, they did not know that Richard Allen Davis had a violent criminal history or that he was violating parole.
Now try to tell me that if you had a daughter go missing and all that was left at the scene was a little bit of saliva on a cigarette butt that you would prefer that the police had no DNA database.
Prop 69 is aa real "long shot" on crime solving.
Previous criminals: you've got their DNA
Non-previous criminals (Suspects): get a warrant for DNA.