Police often use GPS tracking devices to follow suspects, but the law limits how they can gather and use that data. Missouri courts rely on both state and federal rules to decide when GPS evidence belongs in a case and when it crosses the line into an unlawful search.
When police can track a vehicle
Officers usually need a warrant before attaching a GPS device to a vehicle. The U.S. Supreme Court ruled in United States v. Jones that placing a tracker on a car counts as a search under the Fourth Amendment.
Missouri’s Constitution also protects electronic data, which strengthens privacy rights across the state. If officers collect GPS data under a valid warrant, courts may allow the information as long as it meets evidence standards for accuracy and reliability.
What happens without a warrant
When police skip the warrant process, the judge may exclude that data in court. The state follows federal law that treats warrantless GPS tracking as an invasion of privacy. However, judges sometimes allow the evidence if officers acted in good faith or faced an emergency.
Because the law does not yet have a specific statute banning secret GPS tracking, the outcome often depends on how the court interprets the facts and the officers’ intent. In criminal defense cases, these challenges often determine whether prosecutors can use key location evidence during trial.
How courts test GPS reliability
Even when GPS data comes from a legal search, judges still review how officers collected and handled it. Courts want proof that the tracker worked correctly and that no one tampered with the information. Small errors in how police install or monitor the device can weaken the evidence and affect how much weight the judge gives it during trial.
Balancing privacy and investigation
Technology helps solve crimes, but it also challenges privacy protections. State law continues to balance those interests and keeps investigations fair while guarding personal privacy from unchecked surveillance.