One afternoon in August 2012, Mandrel Stuart was driving with his girlfriend into Washington, D.C., when a Fairfax County cop pulled him over on Interstate 66, ostensibly because the windows of his SUV were too dark. Lacking the device necessary to check whether the tinting of the windows exceeded the legal limit, Officer Kevin Palizzi instead cited Stuart for having a video running within his line of sight. While Palizzi was filling out the summons, another officer arrived with a drug-detecting dog. Claiming the dog alerted to the left front bumper and wheel of Stuart's GMC Yukon, the cops searched the car and found $17,550 in cash, which they kept, assuming that it must be related to the illegal drug trade.

Stuart, who had planned to use that money to buy equipment and supplies for his barbecue restaurant in Staunton, Virginia, was astonished that a routine traffic stop could so easily turn into grand theft. But as Washington Post reporters Michael Sallah, Robert O'Harrow Jr., and Steven Rich explain in a revealing and troubling series of stories that ran last week, taking Stuart's hard-earned money was perfectly legal, thanks to civil forfeiture laws that turn cops into highway robbers.

"I paid taxes on that money," Stuart told the Post. "I worked for that money. Why should I give them my money?" Although the financial difficulties that ensued from his encounter with Officer Palizzi forced him to close his restaurant, Stuart ultimately got his money back after challenging the forfeiture in court. Because the government lost the case after a federal trial, it even had to pay Stuart's legal bills, which totaled nearly $12,000.

Other innocent motorists who lose their cash to cops are not so lucky, finding that the cost of fighting a forfeiture leaves them with a fraction of their money even if they convince the government to return it. Since 2001, the Post reports, some 62,000 cash forfeitures have been pursued under federal law in cases that, like Stuart's, did not involve search warrants or criminal indictments. Legal expenses help explain why only one-sixth of those forfeitures were challenged. If the cops take a few thousand dollars from you, it makes little sense to spend thousands of dollars to get it back, especially since there is no guarantee of success and your expenses will be reimbursed only if you go to trial and win.

Three key features of civil forfeiture law give cops this license to steal:

The government does not have to charge you with a crime, let alone convict you, to take your property. Under federal law and the laws of many states, a forfeiture is justified if the government can show, by a preponderance of the evidence, that the seized property is connected to a crime, typically a drug offense. That standard, which amounts to any probability greater than 50 percent, is much easier to satisfy than proof beyond a reasonable doubt, the standard for a criminal trial. Some states allow forfeiture based on probable cause, a standard even weaker than preponderance of the evidence.

The burden of proof is on you. Innocent owners like Mandrel Stuart have to prove their innocence, a reversal of the rule in criminal cases. Meanwhile, the government hangs onto the money, which puts financial stress on the owner and makes it harder for him to challenge the forfeiture.

Cops keep the loot. Local cops and prosecutors who pursue forfeiture under federal law, which is what happened in Stuart's case, receive up to 80 percent of the proceeds. Some states are even more generous, but others give law enforcement agencies a smaller cut, making federal forfeiture under the Justice Department's Equitable Sharing Program a tempting alternative. The fact that police have a direct financial interest in forfeitures creates an incentive for pretextual traffic stops aimed at finding money or other property to seize. The Post found that "298 departments and 210 task forces have seized the equivalent of 20 percent or more of their annual budgets since 2008."

The Fifth Amendment Integrity Restoration (FAIR) Act, a bill introduced by Sen. Rand Paul (R-Ky.) in July, addresses each of these issues. The FAIR Act changes the standard of proof in federal forfeiture cases from "preponderance of the evidence" to "clear and convincing evidence." That change does not go as far as the Institute for Justice, a public interest law firm that has been fighting forfeiture abuse for years, would like. I.J. argues that civil forfeiture should be abolished, meaning that a criminal conviction, based on proof beyond a reasonable doubt, would be required for the government to take property allegedly connected to a crime. But Paul's reform would make it harder for the government to prevail if a forfeiture case goes to trial, which might deter seizures of large sums in situations where the evidence is weak.

Another provision of the FAIR Act probably would not have much impact on cash forfeitures, but it would help innocent owners of other property. The bill requires the government to prove that the owner of an asset allegedly used to facilitate a crime, such as a car or a home, himself used the property for illegal purposes, consented to that use, or was "willfully blind" to it. Current law puts the burden on innocent owners to show they did not know about the illegal use or "did all that reasonably could be expected under the circumstances to terminate such use."

The FAIR Act also would abolish the Equitable Sharing Program, which allows police and prosecutors to evade state reforms aimed at reducing forfeiture abuse. Those reforms include channeling forfeiture revenue to functions other than law enforcement, a change designed to eliminate the profit motive that warps police priorities. Similiarly, the FAIR Act would assign federal forfeiture proceeds, which last fiscal year totaled more than $2 billion, to the general fund instead of the Justice Department.

In addition to the statutory provisions that facilitate forfeiture, several Supreme Court decisions have made it easier for cops to take money from motorists:

Schneckloth v. Bustamonte (1973): Police pulled over a car with a broken headlight and a broken license plate light. When an officer asked if he could search the car, one of the six occupants said, "Yeah, sure." The cops found three pilfered checks under a rear seat and charged Robert Bustamonte, a passenger, with possession of stolen property. The Supreme Court held that a vehicle search based on consent is constitutional even without proof that the person who agreed to the search knew he was free to refuse. In several of the forfeiture cases examined by the Post, police said drivers agreed to allow searches of their vehicles.

Ohio v. Robinette (1996): A deputy sheriff stopped Robert Robinette for speeding. After giving Robinette a ticket, the deputy asked him if he was carrying contraband. When Robinette said no, the deputy asked for permission to search the car, which Robinette granted. The search discovered a small amount of marijuana and an MDMA tablet. Extending the logic of Bustamonte, the Court held that consent to a vehicle search can be voluntary even if police do not tell a motorist he is free to go after he receives a ticket.

Whren v. United States (1996): Plainclothes police officers patrolling a "high drug area" thought a truck was suspicious because it had temporary plates and lingered at a stop sign. When the officers made a U-turn and headed back toward the truck, it suddenly turned right. The cops stopped the truck, ostensibly because the driver turned without signaling and drove at an "unreasonable speed." They caught a passenger, Michael Whren, holding two bags of crack. The Court said detaining a motorist for a traffic violation does not violate the Fourth Amendment's ban on unreasonable seizures, even if a reasonable officer would not have done so without an additional law enforcement objective. The upshot is that police can use alleged traffic infractions such as Mandrel Stuart's tinted windows as a pretext for pulling people over in search of loot.

Illinois v. Caballes (2005): A state trooper stopped Roy Caballes for speeding. While the trooper was writing a warning ticket, another trooper arrived with a drug-sniffing dog, which he walked around the car. After the dog alerted near the trunk, the troopers looked inside and found 292 pounds of marijuana. The Court ruled that "the use of a well-trained narcotics-detection dog…during a lawful traffic stop generally does not implicate legitimate privacy interests." That authorized police to turn any traffic stop into a canine search for drugs like the one that led to the discovery and seizure of Stuart's cash.

Florida v. Harris (2013): A police officer pulled over Clayton Harris's truck because it had an expired license plate. After Harris declined to allow a search of the truck, the officer walked a drug-sniffing dog around the vehicle. According to the officer, the animal got excited and sat down in front of the driver's side door handle. A search of the truck did not find any substances that the dog was trained to detect, but it did turn up 200 pseudoephedrine tablets, along with other chemicals and supplies used to make methamphetamine. The justices unanimously ruled that "a court can presume" a police dog's alert by itself provides probable cause for a search unless the defendant proves the animal is unreliable.

Taken together, these decisions mean a cop can stop vehicles pretty much at will for the sort of minor traffic violations that people routinely commit and then search those vehicles based either on "consent" that may not be truly voluntary or a dog alert that could be inaccurate, imagined, or invented. It is important to recognize that drug-detecting dogs, whether or not they are properly trained, are not nearly as reliable as the Supreme Court seems to imagine. They may react to food and other distractions, legal items that smell like contraband, and conscious or subconscious cues from their handlers, who may be mistaken or dissembling when they report an alert. Vehicle searches based on dog alerts are frequently fruitless, failing to find contraband anywhere from 56 percent to 96 percent of the time, depending on the setting. Even the best-trained dog may be wrong most of the time when it indicates the presence of drugs because the percentage of cars carrying contraband is low.

In Harris, the dog alerted to drugs that were not there. The same thing happened when Mandrel Stuart was pulled over. Recall that a police dog supposedly alerted to the left front bumper and wheel well of Stuart's SUV, implying that he had drugs stashed there. But in the end, the Post reports, the only contraband police found was "a few flecks of marijuana," totaling 0.01 gram, "in the bottom of a bag holding DVDs that were there to entertain Stuart's four kids when he drove them around." Even if we charitably assume that the dog could have smelled that minuscule measure of marijuana while standing outside of the car, that would not explain why it alerted to the left front bumper. Police nevertheless took Stuart's money on the theory that it had something to do with illegal drugs.

In another case discussed by the Post, José Cristobal Guerrero, a legal U.S. resident living in Raleigh, North Carolina, was driving to Mexico when he lost $13,630 to police in DeKalb County, Georgia, after a dog supposedly alerted to his SUV. According to Guerrero's lawyer, the Post says, "The money represented several years' worth of savings and was intended to pay for land in Mexico and bills for Guerrero's extended family there." Although no drugs were found, federal prosecutors still tried to keep the cash "on grounds that it was furnished or intended to be furnished in exchange for controlled substances." They finally agreed to return the money three years later, which never would have happened if Guerrero had not found an attorney who was willing to do the necessary legal work for free. Given the time involved, the lawyer told the Post, the bill would have been around $50,000, more than three times the amount Guerrero was trying to recover.

How sad is it that Guerrero, on his way to a country where police are notoriously corrupt and have been known to shake down innocent travelers, had that experience on our side of the border, where police are supposed to be constrained by constitutional guarantees that protect our privacy and property? Here is a warning the State Department should consider adding to its webpage of advice for visitors to this country: If you travel by car in the United States, don't carry a lot of cash, because the cops might steal it.

This article originally appeared at Forbes.com.