The Crime Prevention Website


The most common method of breaking through a window is by levering it open with a screwdriver, chisel or bar, which is especially easy if the window is only secured with a single handle.  Another fairly common method used on older double glazed replacement windows is to force out the double glazed unit.  Fortunately, as the design of replacement windows has improved over the years, this second form of break in doesn’t happen quite so often.  However, to be certain that your windows will resist these forms of attack when you are having new ones installed, you should make sure that they have been certificated by the manufacturer to PAS 24 2012 Enhanced security performance requirements for doorsets and windows in the UK. External doorsets and windows intended to offer a level of security suitable for dwellings and other buildings exposed to comparable risk.  (Formally BS 7950:1997 Specification for enhanced security performance of windows for domestic applications)  (See  Windows of enhanced security )

When I was a police officer in Acton in West London I would often find myself visiting the victims of burglary offering crime prevention advice.  One of the usual retorts to my suggestion that they fit window locks was “Why bother, they’ll only smash the glass”.  Well that’s true in some circumstances, but actually research tells us that although this does happen it is nothing like as common as you might think.  Perhaps once a week during night duty a caller would ring in to say they had just heard the sound of breaking glass.  Half the time it was a cat falling through a cucumber frame or a ‘domestic’ incident, but the rest usually did turn out to be burglary.   So, yes it happens, but the burglars don’t like doing it. 

Breaking glass takes time, not least the fact that he’s got to smash it all out, but then he’s got to carefully climb through it.  The act of smashing the glass results in the burglar being showered with microscopic shards of glass, which, should he be caught by the police, may allow the forensic experts to match the glass in his clothing to the scene of the crime.  Likewise, crawling through broken glass can leave other valuable forensic evidence behind, such as clothing fibres, shoe prints, fingerprints, leather glove prints and possibly blood, the latter of which could lead to DNA identification.  So the answer to the question “Why bother?” is simple.  Make the burglar smash the glass, don’t just allow him to quietly force the window open.  Also consider the fact that if a window is locked then greater force will have to be applied to overcome the locks.  This means that tool marks left on the window can sometimes be better preserved and can possibly be matched to tools found in the possession of burglars.  In effect then, locking windows prevents a lot of burglary, but should they be overcome the resulting forensic evidence can help the police solve the crime.