A former Land Transport Authority engineer who faced 423 charges of insulting the modesty of women pleaded guilty to 11 counts on Tuesday.

Kew Guozhi, 31, had clipped a camera pen onto his shoelace to take upskirt video recordings of hundreds of women between 2009 and 2010. The 11 charges that the prosecution proceeded related to video recordings of Kew's four colleagues at LTA at the time. They were between 28 and 40 years old.

The other 412 other charges to be taken into consideration involved unknown women at mainly Takashimaya, Kinokuniya, Watson, all at Ngee Ann City, Isetan at Shaw House and other places such as Popular book stores, Ang Mo Kio Hub and Jurong Point.Deputy Public Prosecutor Santhra Aiyyasamy said Kew was detained at Takashimaya store in Orchard Road on Dec 4, 2010 for behaving suspiciously.

An assistant manager who was alerted by a security staff saw Kew squatting at the passage in between shelves of the store and following women wearing short skirts.

After joining a cashier queue behind a woman with short skirt, Kew was next seen squatting again at a passage and fiddling with a device attached to his shoelace.

The assistant manager approached Kew who admitted to taking upskirt photos of women at the store. Police came and seized four recording devices from him.

Investigation showed that sometime in 2009, Kew came across a video in the website showing how to take upskirt videos using a hidden shoe camera. He did some research on shoe cameras and came across a camera pen on eBay and bought it for $50.

He experimented with the camera pen. When he was confident, he bought a few more pens from different sellers on Ebay for taking upskirt videos.

Kew will be sentenced on a later date and faces a jail term of up to one year and/or fine on each charge.