. >> reporter: jennifer lynch, a lawyer saying that mass surveillance has now become affordable. >> it the potential to collect data on a scale we haven't seen so far. if a license plate camera picks up your location many times during the week, it is pin point your path. it can tell who you associate with, which doctor you are going to, whether you are sleeping at a different house every night. >> reporter: the samsy county sheriff's office has just purchased their first mobile alpr. up with of seven they plan to buy. we went along for a test spin. >> oh, here we go. so we just got an alert. so i have to run the plate. >> okay. >> reporter: this time it turned out to be a false alarm. give me a list of some of the crimes you have seen solved because of this technology. >> auto theft, homicide, stocking cases solved. >> is there any question in your mind that this technology is keeping people safe? >> there's no question that it helps police keep communities safer. >> reporter: but in the wrong hands it can reveal intimate secrets. melissa hill is a blogger and privacy activist in minne

. >> reporter: jennifer lynch is the attorney with the electronic frontier foundation a civil liberties organization based in san francisco. >> if you ask law enforcement if what they're doing is legal, they will say well, we have no expectation of privacy in public, but the ability to backtrack through time, to map a car going from one location to another is completely different. with surveillanceamera that can capture 2k5 square miles, it's capturing a lot of people's activities who aren't doing anything wrong, who are innocent citizens. and that's a problem. >> mcnutt believes that persistent surveillance could lead to a lasting drop in crime, but acknowledges privacy concerns. >> there is a tradeoff between security and some aspects of priva privacy. by the fact that we're actually able to provide useful information against multiple crimes and contribute to solving murders to the case you saw, a necklace snatch. that allows us to provide more security with less loss of privacy than any of the other options that are out there. >> i'm sure people once they find out that this experimen

. >> reporter: jennifer lynch is a lawyer with the electronic frontier foundation which is suing the f.b.i. to find out exactly what data the agency is collecting. >> the way that n.g.i. is set up, the f.b.i. said, is they're just including mug shots. but that is really just a policy that the f.b.i. has taken. there's no law that says they have to limit the inclusion of images to mug shots. >> reporter: the f.b.i. acknowledges that its facial recognition system sometimes flags the wrong people. 15% of the time, the suspect won't be among the top 50 hits. >> those people whose face images come up suddenly have to prove their innocence rather than the government having to prove their guilt, and that's completely different, again, from how our democracy has been set up. reporter: privacy advocates worry a growing web of traffic monitors, license plate readers and network security cameras will soon allow police to track our every move, all without a warrant. the legal issues over how these new technologies are used and who has access to all of this information are far from settled. with

. >> jennifer lynch, a lawyer with the electronic frontier foundation says that with alpr, mass surveillancerdable. >> it really has the potential to collect data on a scale we haven't seen so far. if a license plate camera picks up your license plate during the week, it can pinpoint your location and chart your pathway through your life. that can reseal sensitive information. it can tell who you associate with, which doctor you're going to, whether you're sleeping at a different house every night. just north of st. paul, the sheriffs office just purchased their first mobile unit. one of seven the county plans to buy. we went along for a test spin. >> here we go. we just got an alert. i have to run the plate. >> ok. >> this time, it turned out to be a false alarm. give me a list of some of the crimes you've seen solved because of the technology. >> i've seen auto theft solved, homicide solved, stalking cases solved. it provided proof. we were able to show that the stalking suspect had been in the area of the victim's home dozens of times. >> is there any question in your mind that this techn