3D Measurements on Extrusion Marks in Plastic Bags

Abstract

The surface of different types of garbage bags was scanned using non-contact laser profilometry. Manufacturing defects known from visual inspection of the bags (fish eyes, arrowheads, and surface scratches) appear as differences in the height profile. Extrusion lines could only be detected in low-density polyethylene bags. Their correlation length is a couple of centimeters, whereas visually they continue over meters. This can be used to link together the end of one garbage bag with the beginning of the subsequent bag. Extrusion lines are of the order of 0.1 μm for highdensity polyethylene garbage bags.

Stable isotope ratio mass spectrometry and physical comparison for the forensic examination of grip-seal plastic bags

“…Previous research has examined a range of physical and spectroscopic techniques for the classification of plastic films but, in general, has focused on the characterisation of production and handling marks [8][9][10][11][12][13][14]. Although the marks left on extruded plastic by machines are often visible with no enhancement it is generally accepted that birefringence patterns have greater potential for characterising clear plastics as more detail can often be seen using polarising filters [10].…”

A quantitative differentiation method for plastic bags by infrared spectroscopy, thickness measurement and differential scanning calorimetry for tracing the source of illegal drugs

“…Plastic bags are used to conceal body parts of a victim or other crime related materials [1] and to pack illicit drugs [2][3][4] and may be of interest in arson related investigations [5,6]. In particular, a thorough examination of the packaging used to contain drugs can help in tracing their source.…”

A quantitative differentiation method for plastic bags by wide angle X-ray diffraction for tracing the source of illegal drugs

“…Plastic bags may be items of interest for the forensic scientist, for example, if they are used to conceal body parts of a victim or as packaging of illicit drugs [1][2][3][4][5]. Characterization of plastic packaging material may also be useful in arson related investigations [6,7].…”