Hong Kong (CNN) -- Three weeks ago, a man behaving strangely in a city subway station in Hong Kong attracted the attention of police, fearing he may be a terrorist plotting a train attack.
When police searched him, they found he was engaged in terror of another kind -- a camera rigged into the sole of his shoe carried pictures into a hard drive strapped to his thigh, according to local press reports. The suspect was a video voyeur, rigged to take shots up women's skirts.
"We saw the man walking suspiciously and weirdly," Bowen Leung Yiu-kwong, a senior inspector at the police's railway district, told the South China Morning Post. "He was later seen stalking a woman with his leg lifted up."
Hong Kong police have arrested 38 people for "up-skirt" photo taking on the city's Mass Transit Railway, or MTR, during the first half of this year. While that's down slightly from the 41 arrested during the same period last year, the incident shows how sexual predators are using technology to become more creative in their criminal activity.
"Some offenders [commit] 'photo under skirt' crimes by attempting to hide their activities by concealing pinhole cameras inside bags, newspapers, and even shoes which they then activate by way of connecting hand operated leads in their pockets," a press officer from the Hong Kong Police Department told CNN.
Professor Karen Joe Laidler, director of the Center for Criminology at the University of Hong Kong, says these criminals are not opportunists, such as criminals who grope women on crowded trains; rather, they are executing planned attacks.
"The culprits of this type of crime do tend to plan, are creative in their efforts and are generally repeat offenders. There are many websites containing pictures of this type of material, some faked but some real so there is obviously a demand for those types of images," she said.
Depending on what crime offenders taking "up-skirt" photos are convicted of, loitering or disorder in public places, they face a maximum fine of either HK$10,000 ($1,283) or HK$5,000 ($642) and a prison sentence of six months or one year, respectively. Indecent assault such as groping, on the other hand, carries a sentence of 10 years in prison. Official Police Department statistics show that in the first half of 2011 there were 68 reported cases of indecent assault on the MTR, compared with 72 during the same time period in 2010.
"Police deploy a combination of both uniform and plainclothes officers in the railway system in order to provide a high profile overt visual deterrence as well as a covert presence designed to catch offenders in the act, particularly during the busy rush hour periods," a police press officer said.
Police say most indecent assault and "up-skirt" photos taken on the MTR occur in train compartments and on escalators during rush hour. Dr. Laidler noted that "the crowded conditions, the anonymity and ease of escape are all factors" that makes this environment attractive to predators.
In order to deal with the problem of sexual assaults on public transportation, many cities have implemented train compartments reserved for female passengers only. Some public transit systems in Japan began offering "women-only" train cars a decade ago to "prevent groping and other problematic behavior," and to create a sense of safety, according to the Tokyo Metro website.
Seoul is implementing a similar system in the near future in response to a 77% increase in sexual crimes between 2009 and 2010, according to the Korea Herald. Other countries, like Indonesia, Mexico, Egypt and Brazil have also introduced some form of segregated public transportation to deal with harassment. In January Hong Kong's Legislative Council debated the issue of introducing female-only subways cars to the city.
The Hong Kong Women Development Association continues to actively campaign for female-only passenger cars. But Amy Yeung, Executive Secretary of the Association for the Advancement of Feminism, doubted the effectiveness of segregated passenger cars saying their existence may lead to women who ride in non-segregated cars to be blamed if they are harassed. "In countries who have [female only subway cars], there are not enough cars, especially during the rush hour. Females are forced to ride in the normal cars. If they are harassed people say, 'Why didn't you use the special car?'" she said.