There's a new saying in law enforcement circles these days: don't do the crime if your brother's doing time. And the reason for that is the power of DNA.
As 60 Minutes correspondent Lesley Stahl reports, every state in this country collects DNA from convicted felons and loads it into computer databases, all linked together by the FBI. When detectives find DNA at a crime scene, they run it through that database looking for a perfect match. You see this on crime shows all the time.
But sometimes a search yields a not so perfect match but a partial match, in which case it's clear that the felon in the database did not commit the crime. But the DNA is so similar, maybe their father, mother, or brother did.
This raises a dilemma: should police start investigating those family members, or is that going too far?
"These are important scientific leads that need to be run down. And the fact that we can't run them down in this country I think is shameful," says Mitch Morrissey, the district attorney of Denver, Colo.
Morrissey runs one of the most aggressive cold case projects in the country. On three separate occasions over the last few years, his team ran DNA from unsolved rapes through the DNA database and came up with partial hits.
In these three cases, Morrissey says there wasn't a perfect match, but that the matches were very close.
Morrissey wanted the names of those felons, so he could investigate their family members, but he was told that FBI policy prohibits states from sharing names with one another unless it's a perfect match.
"This isn't car break-ins. These are the type of people that will attack women. And continually do it until you catch them. And I think that the FBI, my office, the Denver Police Department, owe it to victims, and potential victims to run down these leads," Morrissey argues.
60 Minutes asked Angelo Della Manna, head of DNA analysis for the state of Alabama, for a crash course in how DNA profiles and matches work.
He showed Stahl the DNA profile of one individual. In a visual profile, one can see 13 pairs of peaks, or "alleles," which are then represented as numbers. One number in each pair comes from the mother; one from the father.
"When you look at this, can you tell me what color eyes that person has, or how tall they are? Or anything like that?" Stahl asks.
"No, not at all," Della Manna says. "The areas that we look at are commonly referred to as in the junk DNA."
When Della Manna runs a sample from a crime scene through the DNA database and gets a perfect match, the numbers are identical in both profiles. But sometimes he gets a partial match, where all but a few numbers are the same.
"These partial matches kind of hit you between the eyes and you say, 'Well, it's obviously not this person.' But when you look at the profile as a whole, there's a lot of sharing there," he explains. "Statistically, there's a strong likelihood that you're looking at the biological relative of the rapist or the source of this crime scene sample."
Criminologists have long known that crime tends to run in families: one study found that 51 percent of inmates in state prisons had a family member who had also been incarcerated. In fact, a statistical analysis last year in the journal "Science" found that if we used our DNA database to deliberately look for family members, it could yield 40 percent more hits.
"Now you're subjecting a whole new class of innocent people to genetic surveillance by the government," argues Stephen Mercer, a Maryland attorney who specializes in issues involving DNA.
"With this new technology, no one has ever considered, 'Well, if my brother's DNA ends up in the database, and he's forfeited his privacy rights by becoming a convicted felon, has he also forfeited my privacy rights, as well, as a wholly innocent family member,'" Mercer says. "That puts me under lifelong genetic surveillance."
Speaking with D.A. Morrissey, Stahl points out, "The other side of the argument is that this is genetic surveillance and that it invades innocent people's privacy. And that this is America and we don't do that."
"Let me give you an example. Say we have a hit and run accident where someone was killed. And we have witnesses that say, 'This is the color of the car. This is the style of the car. But I only got the first three license plate numbers' … Only a partial. What should the police do? Just say, 'Oh no, it's only partial, so we're not gonna do anything.' Or should they go to your motor vehicle database and they may talk to 20 people that weren't involved in the accident at all. And I'll tell ya, most of those people are gonna tell ya, 'Thanks for looking into this. Because we hope you solve the case,'" Morrissey says.