In one of the latest incidents, U.S. District Judge Mark Bennett of Iowa is considering sanctions against prosecutors after a DEA agent failed to disclose that it used a warrantless GPS tracker on a suspect’s car, the website reported.

The judge declared a mistrial in the case in December after the defense raised the issue.

Subsequently, in January the Supreme Court ruled that agencies needed a warrant to use a GPS tracking system in an investigation.

The agent in the the Iowa case, David Jensen, referred in reports to what “surveillance showed” and failed to mention the GPS, the website reported. The judge has ruled that Jensen acted in bad faith by not disclosing use of the GPS.

A hearing on the matter is set for April 30.