A convicted sex criminal who had been sentenced to wear an electronic anklet reportedly attempted to rape a woman before stabbing her to death, police said Tuesday, raising doubts about the effectiveness of the monitoring program.

Police said they have requested an arrest warrant for the suspect, identified only by his surname Seo, who allegedly broke into a house in eastern Seoul on Monday intending to rape the 37-year-old occupant and stabbed her to death when she resisted.

The news of the attempted rape and subsequent murder has stirred controversy over the effectiveness of the electronic anklet system, first implemented in 2008, as the 42-year-old suspect was reportedly wearing a tracking device at the time.

“Unless the court designates a special area to restrict access by ex-convicts, those wearing the anklets can go anywhere they want,” a police official said. “In addition, the anklet system has its limits in preventing crime because the tracking device does not allow us to monitor the convicts’ every move.” (Yonhap News)