A Study On The Unlocked And Broken Traces Of Pin Tumbler Padlocks

With the progress of social technology, it is presented the phenomenon of diversification and specialization when criminals are committing crimes. Some criminals also have a strong sense of anti-detection that they would vandalize and forge the crime scene(the crime scene is hereinafter referred to as the scene). It is rare to see that past popular traditional traces like fingerprints and footprints and so on. While the unlock traces as well as the traces of broken locks appear in the cases, especially in those theft cases, criminals usually ignore the traces because of low popularity. Thus it provides a good opportunity for further investigation of crime scene. The traces of unlocks and broken locks contain large amount of information on the scene, which could provide clues for the investigations and also be helpful for the detections of cases.As a common type of lock in the domestic application, the unlocked and broken traces of pin tumbler padlocks have a high appearance rate. The thesis mainly studies on the traces of unlocks and broken locks about the pin tumbler padlocks in the beginning(the content below are referred to as the unlocked and broken traces of pin tumbler padlocks). The first part will discuss the concept, working principle and the traces during the processing of pin tumbler padlocks; the second part will introduces the formation mechanism of pin tumbler padlocks traces from the view of micro-crystal structure study, material science and engineering mechanics; the third part will discuss the two expression forms of unlocked and broken traces of pin tumbler padlocks on the spot, namely the violent and technological form of unlocks and broken locks. The fourth part will introduces the unlocked and broken traces of pin tumbler padlocks on the spot investigation which is made up of two aspects. The one aspect is the traces in that the criminals use the key to unlock the pin tumbler padlocks and the other aspect indicates that the traces are in the reason why the criminals use some tools to unlock and broke pin tumbler padlocks. The key points and difficult points of this thesis are reflected in the second part and fourth part. It aims to study the formation mechanism of traces of unlocks and broken locks about the pin tumbler padlocks so that people can have further understanding of formation characteristics. At the same time, the author does his best to make an analysis and summarize the expression forms and specific traces of pin tumbler padlocks on the scene, and also researches into unlocks and broken locks’ traces. Then the author will sum up and arrange the characteristics from individual to general which could be a significant help for the spot investigations.