Police will ask 16 railways in the capital area to install surveillance cameras on trains to prevent groping and provide investigators with hard evidence when the crime is actually committed.
Many accused gropers have complained they were wrongfully convicted on the basis of flimsy evidence.
The Metropolitan Police Department, along with the Chiba, Saitama and Kanagawa prefectural forces, will convey the request to East Japan Railway Co. and 15 other railways Monday at MPD headquarters, the police said.
The National Police Agency plans to set up a study group in fiscal 2010 to look into the proposal. The idea of putting surveillance cameras in trains has raised a host of questions about cost and privacy concerns, but the four police forces decided to push the issue, saying they hope the request serves as a "catalyst" for debate.
The police want high-resolution cameras to be installed on the ceilings of the famously crowded train carriages. While admitting the invasive devices may not actually be able to capture gropers' hand movements — which usually take place below the waist — they say footage could show who was standing where during an alleged groping incident.
Groping cases sometimes trigger public inquiries into police investigation methods. In April, the Supreme Court acquitted a college professor accused of groping a high school girl on a packed Odakyu Line train and called for "a careful judgment" in molestation cases because a victim's deposition tends to be the only evidence.