The sight of uniformed police officers holding video cameras is already a common one for protesters, but the use of these cameras remains controversial. Human rights activists say there is no justification for police to tape protests because demonstrators are not committing a crime, only exercising their freedom of expression. Recently, police used videotape footage as court evidence in the first criminal conviction of Falun Gong members in Hong Kong. Sixteen practitioners were found guilty on Thursday of causing a public obstruction during a protest outside Beijing Liaison Office in Western on March 14. They were fined between $1,300 and $3,800 each. Reacting to an earlier police plan to install closed-circuit television cameras in Lan Kwai Fong, the Privacy Commission called for tighter controls over the use of such devices in public areas to protect people's rights. The commission said cameras 'may be appropriate to protect public safety and detect or deter criminal activity' under 'limited and defined circumstances'. In the United States, there is a hot debate over whether the use of surveillance devices to combat crime and terrorism is worth the compromise of privacy and other constitutional freedoms. According to the International Association of Chiefs of Police, CCTV cameras in law enforcement should be used mostly for special events, high crime areas and courtrooms. In Britain, more than 150,000 CCTV cameras are used to monitor public areas. With a powerful zoom lens, the cameras can read the words on a cigarette packet at 100 metres. Trained citizens monitor the cameras and notify police of any illegal activity. Some people support the use of CCTVs, saying they are effective in recording incidents, reducing court time - through guilty pleas - and saving money. However, there are always concerns over privacy and the use of footage for other purposes. Dummy cameras are also used by some overseas police departments, although some critics worry these devices give people a false sense of security. Security at last year's Super Bowl in the US was enhanced by facial recognition technology. Through digital imaging, the cameras were able to compare scanned faces in a crowd to digital portraits of suspected terrorists and criminals.