Research on Chemical Identification Methods for the Formation of Visible Fingerprints on Documents
In civil and economic crime cases,visible fingerprints formed by direct stamping on documents are used to ensure the authenticity of the documents,while indirect copy of fingerprints indicates the pos-sibility of forgery,alteration,or tampering of the documents.Based on the differences of components be-tween direct stamping and indirect copy fingerprints,a chemical recognition method was established to quickly determine the formation method of fingerprints by targeting endogenous amino acids in fingerprint substances and using a highly sensitive specific reaction between ninhydrin and amino acids.The effects of factors were investigated including the formula of ninhydrin,recognition temperature and method,as well as the type of paper,type of printing materials,amount of fingerprint material,and storage condi-tions(dirt,aging)on the recognition effect during the experiments.The results indicate that this method can be widely used to determine the formation method of visible fingerprints on 23 commonly used papers.Sweat stains during normal storage and use of documents do not affect the results of the judgment.Fur-thermore,the formation method of aged fingerprints(naturally aged for 60 days)can be effectively deter-mined by using this method.The method has reliable results,simple operation,fast recognition speed,and a wide range of applications,which is expected to be promoted and used in practical work.
authenticity of documentsninhydrinvisible fingerprintfingerprint formation method
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