PHOENIX — A new challenge has been mounted contesting the legality of Arizona laws that allow police and prosecutors to seize property without proving to a judge it was used for a criminal purpose.

The Institute for Justice is asking a Navajo County Superior Court judge to declare the state’s civil forfeiture statutes unconstitutional. Attorney Paul Avelar contends the laws provide an illegal profit motive for government agencies to take someone else’s property without good reason.

Avelar said the law is also flawed in that it forces someone whose property has been seized to spend money in court to try to get it back. Worse, he said, the statute is worded in a way to chill any such challenge by potentially making the property owner liable for the government’s legal fees.

This is the second such challenge to the laws.

The American Civil Liberties Union filed a similar claim last year in federal court, contesting the actions of Pinal County Attorney Lando Voyles and Sheriff Paul Babeu. A judge has not yet ruled on the case.

Rulings against the counties in either case could portend the end of what has been a controversial practice that prosecutors have defended as a key weapon in their ability to fight crime.

This case involves Terry and and Maria “Ria” Platt, an elderly Washington couple who loaned their vehicle earlier this year to their adult son, Shea, so he could drive to Florida for a vacation.

Avelar said Shea was stopped on Interstate 40 near Holbrook ostensibly because the window tinting was too dark. But after issuing a repair ticket, the officer got consent to use a drug-sniffing dog. A searched turned up a “personal use” quantity of marijuana and some cash.

While Shea was initially arrested, Avelar said there are no pending charges against him. But that did not stop Navajo County prosecutors from moving to seize the vehicle owned by his parents.

Avelar said prosecutors illegally ignored the couple’s legal objections to taking the vehicle and their claims they had no knowledge or culpability for anything their son did.

But he said the problems with the law go beyond this case.

Navajo County Attorney Brad Carlyon did not respond to a request for a comment about the lawsuit.

In general, police and prosecutors have argued that the civil forfeiture laws are important tools in combating organized crime.

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