A federal judge in San Francisco recently excoriated the government over its improper methods in searching one suspect's cell phone and in the use of a stingray to find an alleged co-conspirator.

Prosecutors say the two men, Donnell Artis and Chanta Hopkins, were engaged in credit card fraud and also illegally possessed firearms, among other pending charges that also involve four other people.

The crux of the issue is that, in April 2016, an FBI agent sought and obtained two warrants from an Alameda County Superior Court judge: one to search Artis' phone and another to deploy a stingray to locate Hopkins.

As Ars has reported for years, stingrays are in use by both local and federal law enforcement agencies nationwide. The devices determine a target phone's location by spoofing or simulating a cell tower. Mobile phones in range of the stingray then connect to it and exchange data with the device as they would with a real cell tower.

Once deployed, stingrays intercept data from the target phone along with information from other phones within the vicinity—up to and including full calls and text messages. At times, police have falsely claimed that information gathered from a stingray has instead come from a confidential informant.

Good faith

However, California law does not allow state judges to sign off on warrants for federal agents, something that this particular FBI agent, Stonie Carlson, apparently did not know.

"But the two warrants were plagued by numerous errors, reflecting a pattern of systematic recklessness by law enforcement that militates in favor of suppressing the evidence (and against applying the 'good-faith exception' to the exclusionary rule)," US District Judge Vince Chhabria wrote in a July 3 order. "This ruling is published separately to put the relevant actors in the criminal justice system on notice that California law prevents state judges from issuing search warrants to federal law enforcement officers, which means that federal law enforcement officers are not permitted to execute such warrants."

In a hearing before Judge Chhabria on Tuesday, July 17, prosecutors reiterated that they would seek to appeal his separate order that suppressed evidence obtained as a result of those illegal searches. This process will take months to be heard before the 9th US Circuit Court of Appeals. If this ruling is upheld, it would throw a major wrench into the prosecutions of Artis and Hopkins.

"The good-faith exception to the exclusionary rule does not apply in this case," Judge Chhabria wrote in the second July 3 order. "Perhaps any one of the above-referenced errors, viewed in isolation, could be excused under the good-faith exception. But the whole string of errors embodied in these warrant applications militates against applying the good-faith exception. Indeed, although the above-described errors are the most egregious ones, they are not the only instances of sloppy, inappropriate law enforcement work."

In his orders, Judge Chhabria referred multiple times to a recent stingray case out of Oakland, United States v. Ellis, in which another federal judge definitively found that using a stingray requires a valid warrant.

During a December 2017 hearing, Judge Chhabria also had this incredible exchange with Randall Leonard, an Assistant United States Attorney who argued that because Agent Carlson was part of a sheriff-federal task force, he should be considered a sheriff, with all the rights of a state "peace officer."

Judge Chhabria didn't buy it.

THE COURT: Federal law makes him a sheriff under California law? MR. LEONARD: Well, I mean— THE COURT: So if federal law said that all French poodles are sheriffs under California law, would that be OK? MR. LEONARD: Of course not, Your Honor. THE COURT: There would have to be California law saying, "Yes, we agree that French poodles are sheriffs;" right? MR. LEONARD: Certainly. THE COURT: Otherwise French poodles would not be a sheriff under California law, right? MR. LEONARD: That's right.

“Never before”

The case of United States v. Artis et al. really begins back in August 2015 when Oakland-based FBI Agent Stonie Carlson got involved in investigating Chanta Hopkins, who had an outstanding warrant for counterfeiting issued in Placer County (roughly 100 miles away).

Later that month, Hopkins' Audi, according to Carlson, was seen near Willie Brown's Liquor, a run-of-the-mill East Oakland liquor store—but Hopkins himself did not turn up.

Months later, the FBI learned that Hopkins was providing bogus credit cards to Donnell Artis, who also had an outstanding warrant for his arrest. So the FBI attempted to arrest Artis and found out that he often spent the night at his girlfriend's apartment on Ellis St. in San Francisco, across the bay from Oakland. But on March 24, 2016, when Carlson and his team turned up at her apartment, something strange happened.

"When we approached Apartment 405, I knocked on the door loudly, as I have hundreds of times," Carlson wrote in a November 2017 declaration. "When I knocked, the door swung open as if it had not been latched shut in the first place. Never before in my career had this happened, and its occurrence struck me as troubling and concerning, especially in the high-crime area in which the apartment was located. I immediately began to fear for the well-being of anyone who might be inside. I decided to conduct a safety sweep of the apartment."

The team announced itself and entered, sweeping the girlfriend's apartment to see if anyone was there. The agents found no one. On a countertop, though, Agent Carlson found what he believed to be counterfeit credit cards in Artis' name.

Less than two weeks later, Carlson learned that Artis also liked to hang out at Willie Brown's Liquor, so off he went with another FBI special agent, Brian Koh.

On April 5, 2016, Carlson, dressed in street clothes, went to Willie Brown’s Liquor store and spotted Artis' car. Knowing that Artis had fled police before, Carlson and Koh decided to park nearby and walk up.

"My badge was around my neck but concealed in my hand," Carlson wrote. "I was not wearing any distinctive law enforcement markings. As we approached Artis, he and I made contact. He stepped behind a tree blocking my visual of his whereabouts. SA Koh, to my left, went around the left side of the tree. I went around the right side of the tree. As I came around the tree, Artis had fallen on the ground, and I attempted to subdue him. At around this time, I noticed Artis' phone hit the ground. Artis was able to get to his feet and run across Fruitvale Ave. then across Foothill Blvd. We chased after him. Artis continued northbound on Fruitvale Ave. eventually heading west on E. 22nd St."

Artis got away, but Carlson managed to retrieve the phone—while he had it, Hopkins seemingly called the phone more than once. (Carlson was told by a confidential informant that the phone number of the missed calls belonged to Hopkins.) Later that day, Carlson went to an Alameda County Superior Court judge to get a warrant to search the phone. (However, as Judge Chhabria ruled, this warrant was actually invalid.)

The next day, now that he had Hopkins' phone number, Carlson went back to the Alameda court, this time to authorize the use of a cell-site simulator, also known as a stingray. That way, he hoped, he could locate Hopkins.

Locating the iPhone

Days later, on April 11, 2016, Carlson and the San Francisco Police Department used the stingray to locate Hopkins in an apartment building near the intersection of 1st St. and Lansing St., in the SoMa district. After using the stingray for several hours to try to locate Hopkins' iPhone, law enforcement eventually arrested Hopkins as he exited Apartment 3306 at 45 Lansing St. Soon after, with a warrant to search Apt. 3306, police found cocaine in the freezer, for which Hopkins was also charged.

But Hopkins' lawyer, Steven Gruel, himself a former federal prosecutor, argued that his client's arrest was not only unlawful but that the search of his person and his apartment were illegal. Gruel argued that Carlson was dishonest when he claimed that he saw Hopkins' phone number on Artis' seized phone. Gruel added that Carlson was not forthright when explaining to the county judge what a cell-site simulator actually does.

Worse still, not only did the Alameda County judge not have the authority to sign off on a warrant for an FBI agent, that judge also could not authorize the use of a stingray in an entirely different county: San Francisco.

In short, because Carlson had the wrong type of warrant, that was effectively the same as having no warrant at all—therefore, it was an unconstitutional search. Ultimately, Judge Chhabria found this argument convincing.

"The judge's order suppressing the FBI agent's illegal use of the cell-site simulator to locate Mr. Hopkins is in line with the understanding that we all have a legally recognized privacy expectation in our location," Gruel emailed Ars.

"Whether the FBI uses a GPS or a stingray device to locate someone, the courts are clear that there must be a search warrant supported by probable cause."

Plus, he added: "We had to dig up what the FBI agent hid. There was an obvious effort to hide the truth about using the stingray device to locate and arrest my client."

The United States Attorney’s Office in San Francisco did not respond to Ars' request for comment.

Both sides are due back in court on September 4.