Iowa state troopers stop two California men in a rented car on April 15, 2013. The police stop, search of the car and seizure of more than $100,000 is at the center of a federal civil rights lawsuit in which the motorists claim their rights against unreasonable searches and seizures were violated. (Image from video provided by Iowa State Patrol)

The two men in the rented red Nissan Altima were poker players traveling through Iowa on their way to Las Vegas. The police were state troopers on the hunt for criminals, contraband and cash.

They intersected last year on a rural stretch of Interstate 80, in a seemingly routine traffic stop that would soon raise new questions about laws that allow police to take money and property from people not charged with crimes.

By the time the encounter was over, the gamblers had been detained for more than two hours. Their car was searched without a warrant. And their cellphones, a computer and $100,020 of their gambling “bankroll” were seized under state civil asset-forfeiture laws. The troopers allowed them to leave, without their money, after issuing a traffic warning and a citation for possession of marijuana paraphernalia that carried a $65 fine, court records show.

Months later, an attorney for the men obtained a video of the stop. It showed that the motorists were detained for a violation they did not commit — a failure to signal during a lane change — and authorities were compelled to return 90 percent of the money.

Now the men are questioning the police tactics in an unusual federal civil rights lawsuit. In the suit, filed Sept. 29, William Barton Davis, 51, and John Newmer­zhycky, 43, both from Humboldt County, Calif., claim their constitutional rights against unreasonable searches and seizures were violated. They also contend the stop was part of a pattern connected to the teachings of a private police-training firm that promotes aggressive tactics.

In the wake of Sept. 11, 2001, an aggressive brand of policing called “highway interdiction,” which involves authorities seizing money and property during traffic stops, has grown in popularity. Thousands of people not charged with crimes are left fighting legal battles to regain their money. (Gabe Silverman/The Washington Post)

Davis is a professional poker player, and Newmerzhycky worked as glass blower, according to court records. In an interview, Davis said the men felt as though they were being “stalked” by the police.

If allowed to proceed, the lawsuit could illuminate the widespread but little-known police practice known as “highway interdiction.” The suit names Desert Snow, the Oklahoma-based training firm, and its founder, Joe David, court records show. It also names the two Iowa State Patrol troopers who participated in the traffic stop and were trained by Desert Snow.

Desert Snow’s lead instructor, David Frye, said the lawsuit has no merit and contains “outrageous” and “inaccurate” accusations.

“The evidence will show that the individuals who had their money seized were involved in drug trafficking and that the vacuum sealed packages of cash they had in their possession were tied to the sale of narcotics,” Frye said in a statement to The Washington Post. “Desert Snow is a top-notch training program which will continue to teach officers how to legally and professionally identify and apprehend persons involved in criminal activity.”

The case has created a stir in Iowa’s political and law enforcement worlds. The Des Moines Register wrote about the lawsuit and called for legislative reforms in an Oct. 19 editorial that cited the I-80 seizure and a recent investigation by The Post, which found that police nationwide have seized $2.5 billion in cash from almost 62,000 people without warrants or indictments under federal civil asset-forfeiture laws since 2001. The laws allow police departments to keep up to 80 percent of the cash they seize.

“As long as police agencies know that all or some of the cash they seize will be funneled back into them, the roadside shakedowns are going to continue,” the Register’s Oct. 19 editorial said.

In September, The Post reported that police trained by Desert Snow, along with those who participate in Black Asphalt, an informal police intelligence network started by the firm, said they had seized more than $427 million in one five-year stretch. Among others things, Black Asphalt enables police to share tips across state lines about drivers who raise their suspicions.

The troopers in the Iowa case, Justin Simmons and Eric Vanderwiel, were both trained by Desert Snow, court documents show. They also were members of Black Asphalt, according to internal documents obtained by The Post. They were also part of a drug interdiction unit in eastern Iowa.

A spokesman for the Iowa Department of Public Safety said the troopers declined requests for interviews. In response to inquiries by The Post, spokesman Alex Murphy acknowledged that the troopers were still members of Black Asphalt. But he said they had not submitted any information to the network since 2012, when the department prohibited such reporting because of concerns about civil liberties and “an increased risk for civil and criminal liability for officers and the department.”

An earlier Register analysis last year found that 86 percent of warnings and citations issued by Iowa’s aggressive interdiction units between 2008 to 2012 were given to out-of-state drivers. The newspaper reported that the units seized more than $18 million in drugs and $7 million in cash from 2011 to 2013.

The stop of the gamblers in Iowa on April 15, 2013, illustrates some of the highway interdiction methods in use nationwide.

Earlier that morning, an officer in Illinois alerted an Iowa trooper to a suspicious red car with Nevada license plates driving west, court records show. When the Altima appeared in Iowa, Trooper Simmons followed it for several miles before pulling it over. He told the motorists that they had been stopped for failing to signal when they passed a black SUV.

Simmons said he was issuing a warning for the failure to signal. After handing over the paperwork, he said the stop was over. Then he asked the driver, Newmerzhycky, if he had “time for just a couple quick questions.”

Police who specialize in highway interdiction use casual conversations to avoid triggering legal questions about the length of stops. If the conversations are consensual, courts consider the added delay to be legal.

Highway police are trained to use the chats as an opportunity to take stock of alleged “indicators” of criminal activity, including nervous speech patterns, a pulsing carotid artery and inconsistencies in stories. They are also trained to seek permission for warrantless searches.

“Do you got any drugs?” Simmons asked on the video recording that was later obtained by his lawyer. “Any large amounts of U.S. currency?”

“Absolutely not,” Newmer­zhycky said.

“Nothing in there? Could I search your car?”

“I don’t see any reason to. I’m not going to consent to that.”

“Okay. I’m just asking you if I can,” Simmons said.

“No.”

At this point, the stop is supposed to come to an end and the driver allowed to leave, unless during the consensual conservation the officer has developed a suspicion — one that can be articulated — that a crime has occurred.

Scholars of constitutional law said that a refusal to consent cannot count as suspicious behavior. Nervousness on its own also is not sufficient to justify continued detention, they said.

But rather than release the motorists, Simmons told them he wanted to bring in an officer with a drug-sniffing dog.

“Could I just call him? Do you want to wait? I’ll call him and just run a dog around it real quick.”

“I’d prefer to be on my way. I mean, I’m telling you the truth, there’s nothing in my car,” Newmerzhycky said.

“I’m just asking you if you want to wait for me to run a dog around,” Simmons said. “I’d like to.”

“Do I have the right to say ‘no’ to that?”

“You do.”

“I’d prefer to be on my way.”

At that point, the stop had gone on for almost half an hour. Simmons told Newmerzhycky that you “seem like you were really nervous” and that “I’ve seen your pulse running here.”

Minutes later, Trooper Vanderwiel arrived with the dog, which alerted on the back area of the car. That gave Simmons and Vanderwiel probable cause to search the vehicle without a warrant or the driver’s consent. They found more than $100,000 in cash, most of it shrink-wrapped in plastic. They also found an herb grinder that contained some flakes of marijuana.

“I’ll be honest with you, we didn’t find anything illegal, so you are not arrested, right?” Simmons said on the video. “But you are being detained.”

In a recent interview with The Post, Davis, the passenger in the car, said the men lied because they were concerned the police might take the money.

The troopers took the men to a state highway maintenance facility, where they were joined by two state investigators and continued to question the men about the money and examine the car. Two hours later, they let the men go — without their cash. Newmerzhycky was given a drug-paraphernalia citation for having the grinder, a misdemeanor.

Davis and Newmerzhycky hired a lawyer and challenged the seizure in Iowa, citing the video of the stop. In September 2013, authorities reversed course and cut a deal to give back 90 percent of the money.

That wasn’t the end of it, though. The day of the traffic stop, one of the state investigators had called authorities in Humboldt County, Calif., who raided the men’s homes the next day. They found that each was growing marijuana.

California authorities brought criminal charges against them for unlawful cultivation of marijuana, possession of marijuana with intent to sell, and providing a place for the use, storage, manufacturing of a controlled substance.

But the California prosecutor dropped the charges in April after learning more about the circumstances of the traffic stop.

“We’re moving to dismiss in the interest of justice because the officers that conducted the search warrants here in California were given information from an officer who was out of state,” the prosecutor told a judge in Humboldt County. “The officer who was out of state got it from a traffic stop, but the traffic stop was done without probable cause.”

The prosecutor added: “The People realize that everything else would be fruit of the poisonous tree.”

Their attorney would later note in legal filings that Davis and Newmerzhycky both had permits allowing them to grow marijuana for personal medicinal purposes, court records show.

After the California case was dropped, Davis and Newmerzhycky hired another lawyer, Glen Downey, to pursue the civil rights claims.

Downey said he believes the evidence will demonstrate that the Desert Snow training encourages police to go too far.

“They’re telling these officers how to do it step by step,” Downey said. “They’re giving them a manual on how to violate motorists’ constitutional rights.”

A spokesman for Iowa Attorney General Tom Miller said the office will represent the police in the lawsuit. In a statement, Miller said that “civil forfeiture law is an important tool needed by law enforcement to deny criminals (especially drug dealers) the fruits of their crimes” and that abuses of the law by police are “isolated.”