Wang Mingzhu chats with a vendor at the downtown commercial center of Wuhan. Wang recruits dozens of volunteers, mostly vendors, who help him track suspected pickpockets. Zhang Mingguo / for China Daily

Dressed like a locksmith, Wang Mingzhu arrives at his usual spot in the inner city of Wuhan, capital of Hubei province, at 9 am. But, unlike the usual locksmith, he is more interested in observing the crowds than his business. Wang is a plainclothes policeman.

After two hours, a pregnant woman in red catches Wang's attention, and after the woman passes in front of him, Wang stands up and follows her.

The woman looks around frequently and cautiously, so Wang stops and signals to a "vendor" nearby to take over the stalking.

Roaming around for half an hour, the woman seems to notice that she has been followed and enters a public lavatory. Minutes later, out walks a fashionable woman in gray shirt.

The woman has abandoned her pregnant disguise and changed her clothes to ditch her stalkers. But her trick fails to escape the professional eyes of Wang, who swiftly orders other plainclothes police personnel to track her into a shoe store.

Wang has sound judgment - the woman is a pickpocket. Just as she successfully sneaks a customer's handbag into her backpack and is about to flee, Wang and his colleague nab her on the spot.

How to spot a "fake pregnant woman"? Wang raises his bushy eyebrows. "You can tell from the posture and gait," he says.

As a senior policeman, Wang has been focusing on pickpocketing since 2003. In recent years, Wang has caught more than 2,000 pickpockets.

Every day, Wang and his team patrol around Zhongshan Road, the downtown commercial center of Wuhan, where the high concentration of people and businesses make theft a common occurrence.

"Some people think catching thieves is easy," Wang says. "The job is in fact more technical than that."