Experimental Study Of Characteristic Changes In The Sequence Identification Of Printing And Stamping Due To Oiliness Pigment Infiltration Effect

Sequence identification of printing and stamping is an important content in forensic science. In practice, infiltration effect will course the change of apparent characteristics of crossed stroke and stamp impression. This increased the difficulty of examining crossed sequences. Characteristic changes in the sequence identification of printing and stamping due to oiliness pigment infiltration effect have been a difficult problem in forensic science for a long time. For this reason, this paper carries out an experimental study of the infiltration effect, by means of controlling different seal pigment(inkpad and atomic stamp-ink), different stroke pigment(Electrostatic printing ink and ball pen ink) and different time interval(0 day, 7 days, 14 days and 30 days), meanwhile, observing the changing of characteristics of different sequence. Analysis factor of this phenomenon, summarize the laws for the infiltration effect and explore identification method in allusion to this effect. This paper focuses on the techniques of 3D microscopic method of examining crossed sequences, assist with fluorescence microscope techniques. The result shows that within 30 days, the characters of the crossed stroke and stamp impression have changed on some level, but different sequence still have some different characters which can be used to identify the sequence of printing and stamping. However, after 30 days, compared with it’s initial stage the apparent characteristics of crossed stroke and stamp impression have changed a lot, some key characters which can be used to tell the sequence have lost, it is hard to identify the sequence of crossed stroke and stamp impression. In addition, when printing before stamping, the degree of infiltration is deeper than the case of stamping before printing, and the surface gloss and the condensed state of printing ink can be easily affected by the infiltration. However, the yellow bright spot on the surface is not affected by the infiltration. This yellow bright spot can be identified when printing before stamping, but can not be identified when stamping before printing. The shrink and break of strokes and the completeness of stamping are also remained.This paper analyzed and summarized the changing law of the apparent characteristics of crossed printing and stamping sequences due to infiltration effect. It is undeniable that compared with it’s initial stage the apparent characteristics changed a lot due to the infiltration effect, the time window and methods for identification are limited, further explorations are necessary.