Application of pyrolysis-gas chromatography to car paint analysis for forensic purposes

The fo ren sic ex pert very of ten co mes across car paint traces in the course of case work. These sam ples usu ally orig i nate from the scene of a car ac ci dent or are re cov ered from the clothes of a per son who has been knocked down. The task of the in ves ti ga tor in such cases is usu ally to es tab lish the car make, model and even year of pro duc tion, thus fa cil i tat ing iden ti fi ca tion of the of fender. In such cases it is very of ten nec es sary to per form suit able anal y sis, which al lows de ter mi na tion of the chem i cal con tent of the paint: the type of resin mak ing up the base of the poly mer, in or ganic and or ganic pig ments and fill ers, and also other ad di tives. Such in for ma tion, in con junc tion with data sup plied by road ac ci dent ex perts, is very valu able and can be use ful in in ves ti ga tion. From the point of view of the fo ren sic sci en tist, the most de sir able sit u a tion is where the lab o ra tory has at its dis posal sam ples col lected from both the scene of the car ac ci dent and the sus pect. Com par a tive anal y ses of vary ing de grees of complexity can be per formed in such a sit u a tion, aimed at eval u at ing the sim i lar ity of ev i dence and con trol sam ples. Car paint anal y sis is a rel a tively dif fi cult task. Paint sam ples col lected at a car ac ci dent scene are usu ally very small and have a multi-layer struc ture. An ad di tional prob lem is that they have a com plex chem i cal com po si tion, in clud ing a large num ber of com bi na tions of or ganic and in or ganic com pounds with many me tal lic and non-me tal lic el e ments. Ob tain ing re li able and wide-rang ing an a lyt i cal re sults thus gen er ally re quires ap pli ca tion of not one, but sev eral in de pend ent in stru men tal meth ods. There fore, search ing for new meth ods which al low one to ob tain de tailed in for ma tion about the main com po nents of an ana lysed paint Prob lems of Fo ren sic Sci ences 2005, LXI, 7–18