Lock-picking

An important facet of a forensic investigation is the examination of the crime scene. Attention to all the details can be invaluable in determining the nature and course of the events. One telltale clue to a crime can be signs of forced entry. Crude means of entry, such as the breaking down of a door or smashing of a window, are easy to discern. Lock-picking is less evident.

One of the simplest types of lock to pick is known as a pin-and-tumbler design. This lock uses a row of pins, divided into pairs, which rest in a row of shafts running perpendicular to the clock's main cylinder plug and its housing mechanism. Insertion of the right key forces the top and bottom pins apart at just the right distance so that all of the upper pins rest in the outer housing and all of the lower pins rest in the plug. At that point, no pins bind the plug to the housing, meaning that the cylinder can be turned freely, releasing the bolt that holds the locking mechanism in place.

To open such a lock without a key, one needs a long, thick piece of metal with a curved end (a pick), which can be inserted carefully inside the lock as one would a key. Moving with finesse, it is possible to adjust all the pins into place so that the cylinder can be turned as though the key had been used. Or one can apply a sloppier variation, known as raking, in which a pick is inserted and pulled out quickly with a tension wrench, such as a flathead screwdriver, while the cylinder is turned.

Experienced lock-pickers use a wide array of tools. They are likely to go to work using an entire tool kit with picks, "rakes" (picks for raking a lock), and tension wrenches, all of which are small enough that a basic lock-picking kit could fit into a pocket. To be equipped for a greater range of eventualities, a lock-picker may use a kit that includes other tools, such as a burglar alarm evasion kit, a key-impression kit (for making a key based on impressions that a lock makes on a key blank), a key-pattern device (for copying old-fashioned warded keys, made to fit into lever locks), files, and other items.

Even more sophisticated is an electric lock-opening device, which is used in tandem with a pick to move the pins into the proper position. Additionally, a lock-pick gun can be used to open most pin-tumbler mechanisms. By squeezing the trigger, one strikes the pins with the pick, after which a tension wrench is applied to turn the lock cylinder.

There are other varieties of techniques and tools, just as there are variations in lock design, such as the wafer-tumbler lock, in which tumblers in the shape of wafers take the place of pins. Most aspects of lock-picking are simple in concept, but far from easy in application. It is the less than deft attempt at lock-picking that can leave telltale lock damage as a valuable forensic clue.