Rand Paul has introduced federal legislation to reform civil asset forfeiture. But until that passes, it's best to know your rights. (Andrew Harnik/AP)

Joseph Rivers was never convicted of a crime. He was never charged with one, or even officially detained. But that didn't stop the Drug Enforcement Administration from taking his life savings away under civil asset forfeiture, the highly controversial practice that allows law enforcement officers to take property from people whom they never even charge with a crime.

I spoke with Rivers's attorney, Michael Pancer of San Diego, about the case yesterday. He said the situation Rivers got caught up in -- where federal agents boarded a train and started asking people questions like "who are you?" and "where are you going?" -- is a lot more common than you might expect. "Their purpose is to try to find money to seize or find evidence of criminal activity," he told me. "That's why they do it. But I think the main purpose is to try to find money."

Many law-abiding citizens may not be worried about civil forfeiture laws, because why would police target you if you haven't committed a crime? But when it comes to civil asset forfeiture, it doesn't matter whether you commit a crime or not. If you exhibit certain types of behavior that law enforcement officers deem "suspicious" -- a broad category encompassing everything from having empty energy drink cans in your car to buying a one-way train ticket with cash -- they can use that as a basis for a determination that property you own was obtained through illegal means.

In last year's Washington Post investigation of highway asset forfeitures, experts outlined the contours of law governing these encounters. In a similar spirit, here's what experts say about how the law works in situations like the one Joseph Rivers found himself in.

You should probably identify yourself -- but you don't need to do much more than that.

Pancer says there's some argument over whether you even have to identify yourself if a law enforcement official asks you your name on a train or bus. In some states this is required by law, and in others it's not, according to the ACLU. But it wouldn't hurt to do so just to be safe. Beyond that, you're under no obligation to tell them anything. Not where you're from, where you're going or why you're going there. You don't have to say how you purchased your ticket, or whether it was one-way or not.

"You have the right to remain silent," as they say -- especially if a law enforcement officer just wants to chat.

You don't need to agree to a search.

Joseph Rivers answered the DEA agents' questions. When they didn't like what he said, they asked his permission to search his belongings. He gave it to them, but he didn't have to.

If police ask for one of these "consensual searches," you're under no obligation to give consent. You might get some pushback from the officers. They might threaten to detain you, or to obtain a warrant. But in order to do that they'd need probable cause -- and if you're abiding by the law, and you haven't said anything to them, they have no probable cause to work from.

"It's almost a cliche that a lawyer always tells his client don't cooperate, don't talk," Pancer said. "This is a concrete reason we give that advice."

Be calm, be polite and don't physically resist.

If a police officer attempts to search you without consent or probable cause, that search is illegal. But you won't do yourself any favors by yelling at the officer, or by physically resisting them. It's not up to you to determine whether or not a search is illegal, or whether there was sufficient probable cause -- if things get to that point, the courts will have to sort it out.

Pancer says that when the DEA agents were taking Joseph Rivers's money away, a number of other passengers who witnessed it became upset. "One witness tried to question the agents and was threatened with arrest," Pancer told me.

If you're observing a police encounter like this in public, you can film it.

Cellphone cameras have fundamentally changed the relationship between police and the communities they serve. Where before it was the cops' word against yours, now it's relatively easy for eyewitnesses to produce video evidence of police encounters.

"When in public spaces where you are lawfully present you have the right to photograph anything that is in plain view," according to the ACLU. "That includes pictures of federal buildings, transportation facilities and police."

Just don't interfere with the police -- then they may be legally allowed to demand you stop filming.

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Pancer told me that there may be a silver lining to Rivers's case. "An L.A. talent manager from Detroit, who manages talent in the music video world, read about this story and felt very badly for Joseph. They're in touch now, and he may get some work out of it."

The Drug Enforcement Administration did not respond to a request for comment by the time this article was published.