A federal judge concluded on Friday that a Denver police sergeant interrogated a man who was under arrest for a suspected firearms offense while failing to provide a Miranda warning first.

U.S. District Court Judge S. Kato Crews acknowledged that defendant Dayvon Vaughns may not have said anything incriminating during the questioning, and his statements may have been inadmissible at trial for other reasons. But in a Jan. 3 order, Crews criticized the government’s argument that Vaughns was not being interrogated about his potentially criminal conduct, but rather about the officers’ actions during his arrest.

“It’s a fine line between a police sergeant’s questioning of a 20-year-old suspect who is in custody about his Officers’ conduct, and questioning that suspect about his own conduct, thus risking eliciting an incriminating response,” warned Crews.

Following the landmark U.S. Supreme Court decision in Miranda v. Arizona, law enforcement must advise a suspect in custody of their constitutional rights to silence and to consult with an attorney prior to an interrogation. A failure to provide a Miranda warning may result in the prosecution being barred from using the defendant’s statements at trial.

In April, two Denver officers pulled over a car in which Vaughns was riding. The officers had been following the vehicle from a liquor store parking lot, where they saw Vaughns suspiciously wearing latex gloves and believed the behavior was consistent with drug dealing.

While one officer spoke to the driver about an alleged traffic violation, the other officer became concerned Vaughns’ behavior might indicate a concealed weapon. Upon asking Vaughns to exit the car, the officer allegedly saw Vaughns reach for his waistband. The officer immediately tried to pat Vaughns down, but he resisted and prompted both officers to wrestle him to the ground.

They discovered a semiautomatic handgun in his pants with ammunition inside. A grand jury indicted Vaughns for being a felon in possession of a firearm and ammunition, which carries up to 15 years’ imprisonment.

The defense alleged three constitutional violations surrounding Vaughns’ arrest. First, the initial traffic stop was unreasonable. Second, there was no legal basis to pat down Vaughns for weapons. Finally, the post-arrest interview lacked a Miranda warning.

Crews rejected the defense’s first two arguments. He noted the arresting officers alleged they saw the vehicle speed and fail to signal, providing a basis for the stop. Further, the officers had reasonable suspicion that Vaughns was armed and dangerous, requiring a pat-down search.

Crews agreed with the defense, however, about Sgt. Lex Jorge’s questioning of Vaughns as he was sitting in a police car. Without informing Vaughns of his rights, Jorge asked several open-ended questions about what happened, including one question about the gun.

The U.S. Attorney’s Office argued Jorge made clear he was “investigating his officers, not the defendant.” Moreover, Vaughns had not identified any incriminating statements he made to Jorge that should be excluded from trial.

That may be true, responded Crews. But a Miranda warning is required when police ask questions they know are “reasonably likely” to result in incrimination.

“The open-endedness of these questions risks eliciting statements from Mr. Vaughns about his own conduct or state of mind. The questions are virtually indistinguishable in terms of any focus on the Officers’ conduct versus Mr. Vaughns’,” he wrote. “The Court finds that any reasonable officer in Sergeant Jorge’s position should know that his extremely open-ended questions to Mr. Vaughns were reasonably likely to elicit incriminating responses.”

The case is United States v. Vaughns.