Wrong. Research shows that bigger is only better if DNA databases grow in the right way: by entering more samples from crime scenes, not samples from arrestees. DNA databases already include 10 million-plus known offender profiles. But a database with every offender in the nation cannot solve a crime if no physical evidence was collected or tested. And police collect far too few such samples.
Police do routinely collect physical evidence in cases of homicide and in most cases of rape. But evidence is not collected from eight out of 10 crime scenes for other serious offenses, like burglary, robbery and aggravated assault. Forget what you see on the proliferation of CSI spinoffs. Many jurisdictions do not even have dedicated and trained crime scene investigators.
States like California, which vastly expanded DNA databanks to include arrestees, do not generate dramatically more matches between offenders and crime scenes than do states with much smaller databases, like New York or Illinois. That is because New York and Illinois, despite the smaller numbers of offenders in their databases, enter crime scene samples at rates comparable to California. Indeed, from 2010 to 2012, California halved the average number of offender profiles uploaded per month, but kept the number of samples from crime scenes constant. The result was an increase in database hits. The same dynamic played out in the United Kingdom. The lesson is clear: The police solve more crimes not by taking DNA from suspects who have never been convicted, but by collecting more evidence at crime scenes.
Even worse, taking DNA from a lot of arrestees slows the testing in active criminal investigations. After all, 12 million or more people are arrested each year. (According to one study, by age 23, nearly one-third of Americans have been arrested for an offense, not including minor traffic violations.) Backlogs created by arrestee DNA sampling means that rape kits and samples from convicted offenders sit in storage or go untested. This hurts innocent suspects, like Cody Davis, who was convicted in Florida because of a delay in testing evidence that later cleared him. And although you likely have a right to have your DNA expunged if your arrest was mistaken, in some states it is up to you to petition the court, and needless to say there is no right to counsel or easy online way to carry out such a request.