The examination of disc and pin tumbler locks for tool marks made by lock picks

Microscopic examination of the tumblers of pin and disc tumbler lock cylinders may indicate whether an attempt has been made to pick the lock. If an attempt has been made to pick the lock, it is often possible to determine what type of pick was used. Lock cylinders of five manufacturers, employing tumblers of several different compositions, were examined. The lock cylinders were picked with rake, hook, and bounce picks made of spring steel. The cylinders were disassembled and examined for pick marks. The location and appearance of the marks are discussed. Briefly mentioned are the effects of other types of picks and the effect of ball bearings in the pin wells. Photographs are included to show the pick and wear marks.