ASK! about Anything and Everything

Two-way mirrors allow people standing outside of a room to look in, while the people in the room are unaware, mistaking that piece of glass for a mirror. There are several useful applications for such a mirror. In a therapy session for example, researchers can observe the behaviour of the subjects through a two-way mirror. Two-way mirrors are also used in police interrogation rooms.

With the wrong motive in mind though, this technology becomes a weapon of crime. A man and two women who had rented a room in Colorado realised that the mirror in their shower room was actually a two-way mirror and made a report (3 June 2009, Police investigate two-way mirrors in apartment, AP). Way back in 1996, a couple discovered a two-way mirror in their rented apartment when they noticed a strange red light on it (13 February 1996, Tenant Finds Video Camera in Mirror, The New York Times).

So how do you detect a two-way mirror? Here’s some tips gleaned from news articles. A one-way mirror is usually opaque on one side and clear on the other. To test, switch off the lights so that the room is dark. Take a torchlight or lighter and shine on the mirror. If it reflects back, it is a one-way mirror. If it shines through, then it is likely a two-way mirror.

Also be alert for suspicious lights or sounds that may indicate someone or something (camera) behind the mirror. If possible, move the mirror and check behind for any holes.

References:
1. 20/20 Wednesday Preview High-Tech Peeping Tom, Good Morning America, 27 January 1999, Factiva.com, 25 Jun 09, eresources.nlb.gov.sg/index.aspx
2. US motels subject of more ‘peephole’ lawsuits, Straits Times, 16 September 1992, Factiva.com, 25 Jun 09, eresources.nlb.gov.sg/index.aspx

   Originally answered by Mr Roy Won, Librarian, Adult and Young People’s Services