The generic letters, signed by Dayton police Chief Richard Biehl, warn that prostitution is a “serious offense” that carries potential penalties such as fines, vehicle seizures, incarceration and “John School,” which are mandatory classes for men arrested for soliciting prostitutes.

The letters note that suspects in prostitution-related offenses often will get unwanted public attention because their names, addresses and photos will be released.

The notices read: “While the reason for your vehicle being in this particular location has yet to be determined, it is our earnest hope that it was not for an illegal purpose.”

The letters also say that at least 43 prostitutes in the city are infected with HIV, and many others have not been caught or tested for that deadly disease and other sexually transmitted infections.

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The letters do not always end up in the hands of the people suspected of trying to engage in prostitution. Sometimes, the recipients are spouses or business owners whose vehicles were in the possession of workers when the suspicious activities occurred.

“We take this very seriously, and we are always looking for new and innovative ways to address this problem,” said Dayton police Major Brian Johns, commander of investigations and administrative services. “A lot of times, people don’t realize their cars are being used for illegal activity.”

The Dayton police vice unit, like other police agencies across the country, uses a letter-writing campaign to let people know that officers observed their vehicles engage in suspicious activity that appeared to be related to prostitution.

These campaigns often are called “Dear Johns” initiatives, in reference to to the informal name of male prostitution clients (johns).

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Letter-writing is a preventative measure recommended by the U.S. Department of Justice Problem Oriented Policing Guide, according to a police spokeswoman.

Police send letters to the registered owners of the vehicles, whose cars and trucks were seen in high-prostitution corridors, such as East Third Street, East Fifth Street, Xenia Avenue, North Main Street and West Riverview Avenue.

Street prostitution harms local neighborhoods for a variety of reasons, Johns said, like when male motorists mistake women and girls who are simply walking down the street as prostitutes and try to convince them to get in their vehicles.

Police conduct decoy operations in which an undercover officer poses as a prostitute, and sometimes the officer draws interest from or interacts with potential customers who do not complete the illegal transaction of sex for money, Johns said.

Letters are sent to the owners of vehicles whose drivers nearly took the bait during these sting operations, police said.

“We don’t send a letter to any car that drives down the street — we have certain parameters that we use, because we don’t want to send letters to vehicle owners whose cars are not being used for that,” he said.

However, one local man who received a letter in the mail bristled at the idea that he was downtown for illegal activity.

The man, who declined to be interviewed on the record by this news organization, said he was in town for legitimate business, leaving a Dayton Dragons game, and that he did not appreciate the letter that implied he was engaged in wrongdoing.

Dayton police responded to more than 60 incidents of prostitution or assisting or promoting prostitution this year, through early July.