One of the most powerful crime-fighting tools in the world could be sitting in your pocket.Police Dog Sniffing Bag

Smartphones can share evidence of crimes as soon as they happen.

Just a few months ago, Boston Marathon spectators provided invaluable photos and videos to help police investigate the April 15 bombing.

“Too often we talk about the ‘bystander effect’ — people watch things happen but don’t get involved,” Radford University criminal justice professor Tod Burke told Business Insider. ”This is a way for people to be the eyes and ears of the police.”

There are now crime-fighting apps that make helping cops even easier.

The Santa Cruz police department was one of the first police forces in America to adopt smartphone technology, creating a consumer-focused free mobile app in 2011. The NYPD soon followed suit early this year. Users of both apps can access the departments’ social media pages; view important alerts, like the wanted list, and crime maps; leave tips; and look at photos and videos.

Law enforcement outside the U.S. also use apps to communicate with citizens. London police used an app called FaceWatch to try to identify people who committed crimes during the city’s 2011 riots. That app let smartphone users view police photos and contact the police directly if they recognized a perp.

Apps like these can help police even if reports don’t lead to an arrest or indictment.

“If a crime goes unreported, for all intents and purposes, it never occurred,” says Burke, who’s also a former cop.

Incident data creates more accurate crime maps. If a pattern emerges, police can dedicate more resources to certain areas.

“It’s not about how many officers you have, it’s what you do with them,” Burke added.

Here are some of the more useful crime-fighting apps:

  • iSpotACrime allows users to upload photos and videos, add voice comments, and pinpoint their locations through GPS. There’s also a panic button for emergencies. Loud noises can deter criminals because the racket draws attention, increasing the chances they’ll get caught. One catch: you must upload your local PD’s email address to get past the welcome screen. Surprisingly, New York City doesn’t have one.
  • Tip Submit offers the same services as iSpotACrime but allows users to specify where they want the tips sent. For example, users can report a crime to federal and local agencies as well as schools within the network.
  • iWitness acts a “virtual witness” to crimes. A blinking light signals that the app is armed. If you feel threatened, a simple touch of the screen does three things: your phone emits a steady light, audio and video recordings begin, and the app records your location. The GPS coordinators, along with recordings, go to a secure server local police can access. If the situation escalates, a second touch calls 911, alerts up to six previously set contacts via text message, and sounds a loud alarm.
  • CrimePush has similar features: It direct-messages your location to the authorities, calls 911, notifies family and friends, and uploads crime reports. The app’s creators provide a disclaimer: the app may not connect users directly to the police. Reports and emergency notifications will only go to agencies that have already integrated with the app.

Apps like these can also improve the quality of crime reports because they’re not just relying on the human eye.

“We all know eye-witness identification is crap,” Burke said.

While these apps all suggest they’re making America a safer place, not everybody is a fan of crime-fighting apps. Rutgers University School of Criminal Justice Joel Caplan doesn’t know if any evidence apps actually decrease crime, and he fears the apps may even give users a false sense of security.

“Do you want to be attacked and record the crime, or do you want to be safe? The better option is to get away from the threat and call emergency services,” he said. With the uptick in “apple picking,” or iPhone and other smartphone theft, flashing your device in public could also invite somebody to steal it.

But if someone does steal your iPhone, as the saying goes, there’s an app for that.

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