Biddle said he is "very concerned" about police actions in cases such as Williams', even when claimants ultimately prevail.

"No contraband or illegal substances are found in the car," he said, but "substantial amounts of cash are seized from the driver or the passenger."

Russo said state troopers are trained to conduct a proper search and seizure of a vehicle, and that people who carry large amounts of cash and whose explanations police find unsatisfactory are often linked to drug trafficking.

"In a lot of cases," she said, "money that can't be documented, especially large sums of money that can't be documented when asked on a traffic stop ... can lead to the uncovering of a crime that is occurring."

Sometimes, Rosenstein said, there are reasons prosecutors might not bring criminal charges — to protect an informant, for example — but will still seize money, cars and property. Those who try to reclaim property in such cases have no Fifth Amendment right to remain silent, he noted, and some do not come forward to be deposed.

Biddle said it is difficult for most people to understand the process for making a bid to reclaim property. Filing a claim even a day late means the money or property is lost.

"I have seen on a number of occasions people whose money is lawfully obtained lose their money because they misunderstand the form," he said.

But Worrall said the 2000 law has limited abuses in the system. Police can put the money to good use funding drug task forces and other complicated efforts.

"With rare exceptions," the professor said, "they're not buying toys and padding their wallets."

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Civil asset forfeiture process

•Property — car, watch, jewelry, cash or home — is seized during a search.

•The government publishes notice asking owners to come forward.

•If someone makes a claim, their property is given back or a court case is opened.

•The owner makes a settlement with prosecutors or their property is forfeited outright.

By the numbers

$4.7 billion — Value of assets taken by federal agencies in fiscal 2012

$17.5 million — Maryland's contribution to a federal forfeiture fund

$6 million — Value of payouts to Maryland police agencies that helped take assets

48 percent — Civil cases closed in Maryland in 2012 in which government kept property without criminal conviction

Sources: U.S. Department of Justice, Department of the Treasury and Baltimore Sun research