Say police are looking for a bad guy who committed a bad crime: Joe Smith, brown eyes, brown hair.
By chance, you happen to be a Joe Smith, brown-eyed and brown-haired, though you haven't done anything wrong. You get arrested anyway.
Police take your fingerprints and, under a new law, swab inside your cheek for your DNA, which they will deposit in a state database.
Our bad, they say when they realize it's a case of mistaken identity and let you go.
But they've got your DNA to check against future crimes anyway.
That's one example of the potential trouble with a new law our governor signed this week requiring police to take a DNA sample from anyone arrested on a felony charge.
This law, to be slowly phased in over several years, would greatly expand Florida's DNA database, which currently has more than 500,000 samples and serves as an extremely useful investigative tool for nailing bad people like rapists and murderers.
So what's the problem?
"Arrested" and "convicted" are two very different things in a nation where we're supposed to be big on innocent unless proved guilty.
Most states already take DNA from convicted felons, as they should. If you're officially guilty, you have to hand over that personal and telling information for future investigative use, period.
But somebody just under arrest?
It's important to note that police have, on occasion, nabbed the wrong guy.
Charges get dropped.
With your DNA on file, you're an automatic potential suspect for future crimes anyway. There's a petition process to get out of the database, but not automatic removal.
So maybe you're thinking: I'm a law-abiding sort of person who is not particularly worried about the kind of things that tend to raise eyebrows over at the American Civil Liberties Union.
What do I care if the government has my DNA if I don't plan on committing any crimes?
Here's one good argument for you: Unlike simple fingerprints, your DNA contains a wealth of information about you, like who you're related to or whether you're at risk for certain diseases.
Presumably, your DNA will be shared between police agencies. And databases containing warehoused information — even databases under the watchful eye of our very own government — can be subject to security breaches.
As the ACLU points out, imagine your personal DNA information in the hands of, say, an employer or insurance company in the position to deny you a job or coverage.
Police, by the way, already can get permission from a judge to take DNA from a suspect if they have well-founded reasons.
Same with wire taps — useful investigative tools, no question, but also intrusive enough to require serious consideration and oversight to protect the public and ensure no one gets overzealous in the interest of solving crimes.
Similar laws have been challenged, upheld and struck down, in other states.
Expect much interest here in Florida.
Yes, we should support arming our police with every useful tool, as long as that's carefully balanced with the rights of the innocent.
Including the presumed innocent.