Li Biao
Department of Document Examination, China Criminal Police University, No. 83 Tawan Street, Shenyang 110854, China.
Forensic Sci Int. 2014 Jan;234:126-31. doi: 10.1016/j.forsciint.2013.10.016. Epub 2013 Nov 15.
In many criminal and civil cases in China, the most commonly questioned documents are those written with gel pen ink. An important task for forensic document examiners is to identify whether two or more ink entries in one or more documents were written with the same ink type. The identification of the age of gel ink entries made poses an important and difficult problem for forensic document examiners. In this paper, a dissolution-diffusion method was successfully employed to estimate the relative age of gel ink entries by comparing dissolution-diffusion rates. Using extensive tests, the mixed solution of dimethyl formamide (DMF) and anhydrous ethanol proved to be a suitable solvent and was used to dissolve the dye of gel ink strokes made at different times. As preliminary findings of this study, calibration curves were created to indicate the relationship between the average dissolution-diffusion rate of soluble gel ink components and the age of gel ink entries stored under natural aging conditions. It was also determined that brands of gel inks, types of paper and thickness of gel ink strokes had varying impacts on estimating the dates of gel ink strokes. Experimental results showed that dissolution-diffusion method was applicable for determining the relative age of gel ink entries under certain conditions.
在中国的许多刑事和民事案件中，最常受到质疑的文件是那些用中性笔墨水书写的文件。文件检验人员的一项重要任务是确定一份或多份文件中的两个或多个墨水痕迹是否使用了同一种墨水类型。确定中性笔墨水痕迹的书写时间对文件检验人员来说是一个重要且困难的问题。本文成功采用了一种溶解扩散方法，通过比较溶解扩散速率来估计中性笔墨水痕迹的相对书写时间。通过大量测试，发现二甲基甲酰胺（DMF）和无水乙醇的混合溶液是一种合适的溶剂，用于溶解不同时间书写的中性笔墨水笔画中的染料。作为本研究的初步结果，绘制了校准曲线，以表明可溶性中性笔墨水成分的平均溶解扩散速率与在自然老化条件下保存的中性笔墨水痕迹书写时间之间的关系。还确定了中性笔墨水的品牌、纸张类型和中性笔墨水笔画的厚度对估计中性笔墨水笔画的书写时间有不同的影响。实验结果表明，溶解扩散方法在一定条件下适用于确定中性笔墨水痕迹的相对书写时间。
