To authenticate Global Positioning System (GPS) tracking data for use in an Article 112a (drug offense) prosecution, the government must lay a proper evidentiary foundation to show that the data is reliable and accurate. This is typically done under Military Rule of Evidence 901, which requires evidence sufficient to support a finding that the matter in question is what its proponent claims. The prosecutor cannot simply present a map with a dot on it; they must prove the data’s integrity.
The foundation is usually laid through the testimony of a qualified witness, often the law enforcement agent who placed the tracker or the technical expert who analyzed the data. This witness must explain how the GPS tracking system works. They need to testify about the specific device used, how it was attached to the vehicle or person, how it transmits data to a server, and how that data is stored and retrieved. They must also testify that the device was functioning properly during the period in question.
A military defense attorney will challenge this foundation. They will cross-examine the witness about the device’s potential for error, its calibration history, and any known vulnerabilities in the system. They may hire their own expert to analyze the raw GPS data for anomalies or inconsistencies. The military judge acts as the gatekeeper and will only admit the GPS data as evidence if the prosecution has successfully laid a foundation that demonstrates the system and the data it produced are sufficiently reliable to be considered by the court-martial panel.