JEFFERSON CITY — A measure before the Missouri Legislature would require a warrant before police could use a device referred to as a “StingRay” to intercept cell phone calls from anyone making or receiving a call near the device.

Currently, Missouri has no law restricting the devices. The American Civil Liberties Union reports police in 23 states, including Missouri, have used cell site simulators.

The simulator mimics a cell phone tower which causes mobile devices in the targeted area to use the simulator device to relay calls. Whoever is operating the simulator device can capture information from cell phone transmissions including data, voice calls, locations and subscriber identity information.

The St. Louis Post Dispatch reported that local police were required to sign a non-disclosure with the FBI before receiving approval to purchase simulators such as StingRay. In some cases, police have dropped criminal cases before defense lawyers and judges can comment on the use of cell site simulators.

Sen. Will Kraus, R- Jackson County, drafted a bill that includes regulations on the use of simulator devices.

The bill would require warrants of probable cause to believe that criminal activity will be or has been committed, or if new evidence can be provided in an investigation.

The authorization of the device’s use would be limited to a time period specified by the warrant. Information gathered from the person of interest would be disposed of after thirty calendar days, and any data gathered from citizens outside the warrant would be erased immediately.

Kraus said his bill will protect residents’ Fourth Amendment right against unreasonable searches and seizures.

“I’m for the police, I want to make sure they have the tools that they need to protect us as citizens, but I’m also about our personal liberties and our personal freedoms, and I want to make sure that we have a fair balance,” Kraus said. “They can do their job, we still have rights.”

Faced with growing national criticism about the devices, the federal Department of Homeland Security adopted rules that include seeking warrants as well as requiring training to properly use cell simulators.