Computer interfaces to measure and record human movement are becoming more common. These recorded measurements can be analyzed forensically to help identify people.
Microsoft is about to launch Kinect, a technology for detecting and interpreting the movement of humans in a defined space, like a living room. Initially Microsoft will apply the technology to its Xbox game console, so that players can interact by moving their bodies rather than moving a joystick or a wii-mote. With time, however, Microsoft envisions Kinect gathering human input in many computing environments.
Even though Kinect may today not be intended for biometrics, it will be capturing biometrically measurable information about the movement of people. To one degree or another, the way an individual moves (walks, swings her arms and so on) is unique. If Kinect is capturing and measuring movements, it is inevitable that the measurements will be recorded.
If records exist, then it is only a matter of time before they become the subject of an investigation into who was interacting with a certain computer at a certain place and time. Cell phones and toll road tags were not intended to track the whereabouts of users. But they collect a lot of data about the location of people at particular times, and that data became irresistible to divorce lawyers and criminal investigators, who, using the power of law, were able to demand access to the data.
Imagine an interactive display in a shopping mall. As patrons walk by, they can interact with the display by dancing, jumping or waving. But eventually there will be an investigation into whether Joey walked by that display (on his way allegedly to rob a store), and authorities will access the data for analysis.
Other sources of measurements for human movement are the accelerometers in iPhones. They have been used to measure, for example, the gait of the person holding an iPhone. If those measurements can be captured, someone can write an app to record them. Then, contrary to the intention of the app writer, some investigator will lawfully tap those records in e-discovery to find out who was using the iPhone.
Behavior biometric measurements are not, by themselves, highly reliable identifiers of individuals. However, the measurements can be forensically meaningful. When combined with other indicia of identity (such as eyewitness identification), biometric measurements can help to pinpoint someone.
Behavioral biometric records will be a new privacy battleground in coming years.