Chicago has decriminalized possession of marijuana, but that doesn't extend to open pot smoking. View Full Caption shutterstock

CITY HALL — Confused about Chicago's marijuana laws, visiting Deadheads?

There have been changes in recent years in both the city's marijuana laws and Cook County's prosecution policy.

Here's the bottom line for first-time or second-time offenders: You can still get arrested — and miss the show — if you are caught in the act of smoking pot. But it's unlikely that prosecutors will follow through on the charges by the time you get to court.

If you're caught holding pot, you could also get slapped with a ticket from a Chicago police officer. Getting a ticket will keep you out of jail, but it will cost you some cash. The decision on issuing a ticket for people caught with less than 15 grams rests with the officer who catches you.

Here's a breakdown:

Chicago three years ago passed marijuana reform laws allowing for tickets to be written for possession of less than 15 grams. The reforms set tickets at $250-$500 for possessing a quantity that translates as up to 25 cigarette-sized joints.

Pot smoking in public still can lead to an arrest if an officer opts makes that call. But the Cook County state's attorney's office is going to drop misdemeanor charges if you've been busted less than three times.

According to the city ordinance, arrests are also called for in the case of possession near schools and on parkland. Soldier Field, the site of this weekend's Grateful Dead reunion shows, sits on Chicago Park District property.

Ted Cox discusses the city's marijuana laws:

Earlier this year, however, the county's top prosecutor, Cook County State's Attorney Anita Alvarez, said her office is changing the way it takes on low-level marijuana possession cases.

People arrested on misdemeanor charges with less than 30 grams of pot will no longer be prosecuted if they have fewer than three arrests or city tickets for marijuana possession.`

People with three or more marijuana arrests on their record would get sent to the state's attorney's drug abuse treatment program if they have no significant history of violence.

“The methods in which we are handling low-level drug cases here in Cook County are simply not working," the state's attorney said in April. "Under our current policies and practices, we continue to see the same individuals revolving in and out of our criminal justice system with no meaningful impact or outcome and at a significant cost to taxpayers.

“While our financial resources are shrinking in Cook County, violent crime is not. These policy changes will enable us to reallocate our resources away from offenders who are nonviolent and have a drug addiction toward fighting violent crime, such as drug trafficking, illegal guns and gangs.”

The enforcement of Chicago's evolving marijuana laws has been uneven neighborhood to neighborhood, according to a Roosevelt University study and media reports.

More recently, Chicago police have claimed progress in treating pot cases equally, for instance dropping a requirement that called for arrests in cases where suspects could not produce an ID.

But while officers have considerable leeway on whether to ticket or arrest, Chicago Police Supt. Garry McCarthy pledged Tuesday that police would be "aggressively enforcing" park rules over the Fourth of July weekend.

While the city's police superintendent specifically mentioned public drinking, zero tolerance could extend to open pot smoking as well.

And there has been no softening of penalties for possession or use of harder drugs.

So, yes, there naturally will be strength in numbers in sparking up at an outdoor concert — especially the three Grateful Dead shows starting Friday, the band's "Fare Thee Well" swan song after forming 50 years ago — but that doesn't mean a police officer can't come down hard if he or she so desires.

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