When Chinese dissident Hu Jia found that the rear tires of his car had been slashed, his disappointment gave way to hope because one of eight police surveillance cameras watching his apartment was pointed at his car.

"I thought, 'Great, no one else has such advantages, I can ask the police for evidence,'" Hu, 39, says.

But the neighborhood police station in Hu's Freedom City apartment complex saw nothing.

"Those infrared cameras feed directly to the public security bureau," Hu said he was told. "That camera is to watch a person called Hu Jia."

Video surveillance is a booming, multibillion-dollar industry in China, bankrolled by an authoritarian Communist Party that has overseen more spending on domestic security in recent years than national defense.

Among the examples, according to the Chinese Ministry of Public Security and others:

- 20 million-30 million surveillance cameras are used in China; 13 million were installed in 2011, and installations will jump 20% a year for the next five years.
- 800,000 surveillance cameras (half for government use) have been installed in Beijing, exceeding London, one of the West's most watched cities.
- The Chinese government spent $16 billion from 2009-2011 to build video surveillance networks nationwide.

Authorities justify the expansion and upgrading of network security cameras as a way to improve public safety, crime-fighting, traffic management and "social stability," an obsession of the Communist Party rulers.

Human rights groups say the cameras are increasingly relied on to monitor and intimidate political dissidents, and China's two most restive ethnic groups: the Tibetans in the southwest and Uighurs in the northwest. China's video surveillance technology has grown more sophisticated, focusing on biometrics research...