BALTIMORE -- If you've ever wondered where police get their military-style tanks or grenade launchers -- or even those fancy new high-tech body cameras -- there's a good chance your local sheriff was pitched by a company here at the annual National Sheriffs' Association (NSA) conference, the country's largest trade show for cops, which kicked off Sunday evening in Baltimore. 

Sheriff John Aubrey from Louisville, Kentucky, welcomed attendees at an opening reception, personally thanking both Verizon and Cisco, which each spent well over $30,000 to sponsor this year's event. 

Every year, taxpayers spend about $100 billion to fund police forces across America. In fact, public expenditures on policing "more than quadrupled between 1982 and 2006," according to data from the U.S. Department of Justice’s Bureau of Justice Statistics. 

That sort of spending has created a massive boom for companies that provide products and services to police and jail adminstrators around the country. And the best place to show off the goods are at this massive trade show, being held this year in the 1.2 million-square-foot Baltimore Convention Center, right next to Camden Yards. 

 "Your competition will be there, and so should you!" the organizers note on their website. 

The location of this year's display of technology and firepower is auspicious. The failings of Baltimore's own policing came sharply into view after the death of Freddie Gray in April, killed by what the medical examiner is calling a "high-energy injury" to his spine during a ride in a police van. The death of Gray, who was arrested for carrying a switchblade, triggered days of protests and unrest around Baltimore and showed how deeply fractured the relationship is between the police and the community, a problem that armored vehicles and high-tech surveillance equipment won't fix (and, in fact, may actually exacerbate). 

image5 A police tank on display at the National Sheriffs' Association conference in Baltimore, Maryland. Photo: Eric Markowitz

Conference attendees include sheriffs and their staff, as well as jail adminstrators, members of the FBI, the U.S. Marshals office, the DEA, police chiefs and U.S border control and customs agents. In total, there are about 4,000 attendees. According to the NSA, the expo has been a sold-out show for the past 14 years. 

Vendors at the conference pay $1,950 for a 10' x 10' booth, plus $150 premium for corner booths, including a $500 non-refundable, non-transferable deposit. About 330 businesses are exhibiting this year, ranging from historic American brands like Smith & Wesson, the gunmaker, to a new breed of upstart technology companies, like CellSens, which claims to be able to root out cell phones hidden inside an inmate's body.

There's even a company that sells e-cigarettes exclusively to inmates. 

In local municipalities across the United States, sheriffs, who are elected officials, are typically in charge of making purchasing decisions for their local police forces and county jails. Though the contracts need to be approved by county commissions, attracting the attention of a sheriff is often the first step in landing a deal. 

Naturally, the American carmakers, including Ford, GMC and Chevrolet, were all on hand selling heavy-duty police cruisers.

image2 E-cigarettes for inmates are a hot new item at the National Sheriffs' Association conference. Photo: Eric Markowitz

For exhibitors willing to spend extra, sponsorships are the key to attracting real attention. 

Verizon, for instance, spent about $25,000 to host an invite-only dinner, which included members of the NSA's executive committee. Taser paid $5,000 for the privilege of hosting a welcome reception.

And the Harris Corporation, maker of the highly controversial Stingray, which police use to eavesdrop on cell phones, paid $5,000 to get their logo onto the conference's hotel keys.

The expo, of course, is more than just a sales pitch. Sheriffs and their staff network and mingle. Sunday morning, for instance, began with a morning prayer worship. On Tuesday, spouses of the sheriffs have the option of attending a brunch -- for $45 a head. 

Throughout the day, speakers have been invited to host "breakout sessions" in conference rooms scattered throughout the hotel. The panels range from discussions like "Seminar N4: Investigating Mass Murderers," to "Seminar 05: How to Deal with the Worst Employees." ("All agencies have employees who are challenging..." the brochure reads, "but few know what to do with these people.")

At the end of the day, though, it's all about the sales pitch. 

On its website, the NSA notes that it hopes to provide "the optimum sales environment for both you and your customers – the sheriffs of the U.S. – because we know that our buyers really mean business."

Unfortunately for all attendees, no company stepped forward this year to sponsor ice cream in the exhibit hall, which would have cost $2,500.

But there's always next year. Specifically, in Minneapolis, where the NSA will hold its 76th annual trade show in June 2016.