Valley police call them the junior varsity of street gangs.
Party crews are groups of teenagers who move from city to city setting up in vacant homes, businesses, warehouses, the middle of the desert or even taking over a smaller party and making it their own.
Police say party crews have been growing in popularity for the past few years. The crews partner to organize and advertise a party. They charge a few dollars at the door and often provide a keg of beer and a DJ.
But police say they aren't just kids being kids. The crews' parties can lead to numerous crimes - everything from underage drinking and vandalism to assaults and shootings.
"It just makes life miserable for the people in those neighborhoods," said Lt. Fred Zumbo, who heads up a gang-enforcement unit for the Arizona Department of Public Safety.
Phoenix police Sgt. David Albertson has been leading the party-crew patrol in the Maryvale district for the past several months.
He can drive around the neighborhoods of south and west Phoenix and point out homes that are past sites for crew parties. He knows all the signs.
One Saturday night in February, when he saw several teenage boys piling into a car just before 11 p.m., he said, "Those kids are getting ready to go to a party."
The action usually doesn't start until after midnight, when police start getting calls about noise or teenagers entering a vacant home.
On this night, police located a party and moved in minutes too late. A party crew had entered a vacant home, set up shop for a while and then left. By the time police moved in, a train of 30 cars was leaving a neighborhood near 77th Avenue and Mulberry Drive.
But Albertson's squad kept watch and stopped cars for minor violations, such as throwing a bottle out a window. In the end, the officers recovered five guns and made arrests for weapons violations, possession of marijuana and cocaine, and liquor and curfew violations.
But this was a slow night for Albertson and his officers. On nights that they bust up the parties, they come away with 60 or more arrests.
Party crews began cropping up in the past few years, authorities say, and they're continuing to gain popularity. Police aren't sure why they're becoming such a problem now.
"It's hard to say," Zumbo said. "A lot has to do with the economy, and a need to generate revenue for illegal activities," such as buying guns and drugs. "It's just really hard to say why they've exploded."
Party-crew members typically end up on one of two courses, police say: they graduate to street gangs or they grow up and get out of the scene.
Party crews are sometimes reclassified as street gangs if they commit a felony.
Although some Valley cities, such as Mesa, are cracking down hard and driving crews out of their neighborhoods, the problem isn't going away. Often, it simply shifts as the crews move to neighboring cities, police say.
New crews develop all the time as teens break from one crew to form their own.
"Are you displacing it or are you making it go away?," Albertson said. "Maybe a little bit of both."
But even though police may never eradicate party crews or prevent teens from experimenting with alcohol, they say they will still do what they can to minimize the effects of the crews, Albertson said. He said they also hope that the arrests will open parents' eyes to what their children have been doing.
"As long as there is this age group and demographic, they will attempt to find a way to consume alcohol and hang out with their friends," Albertson said.
"Where we make a difference is when we remove them from the environment, at least for a night. It prevents them from either victimizing someone else or becoming a victim themselves."
A police helicopter hovers over a Phoenix home where police say they discovered a party crew.
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