Study of Latent fingerprints that are invisible to the naked eye on Various Types of Paper by Iodine and Ninhydrin Test

Benjasine Laowongsee, Nich Wongsongja, Narong Kunides


The purposes of this research were study of latent fingerprint from blood on various types of paper and comparative on the detection of fingerprints on paper with different blood concentrations by iodine and ninhydrin test. This research is experimental research by 10 samples of paper; Copy Paper, Green Read Paper, Newspaper, Corrugate Box, Lottery Ticket, Magazine Paper, Cash Bill, Envelope, Thermal Slip Paper and Brown Envelope after than make the right thumbprint on the paper and then drop the pork blood on the prepared sample paper. In different concentrations is normal pork blood, 1:5 1:10 and 1:100 and then the samples found the latent fingerprint by iodine and ninhydrin test and took a photo latent fingerprint that appeared to count the number of critical points or minutiae with Automated Fingerprint Identification System (AFIS) at Central Police Forensic Science Division 7, Office of Forensic Science. The results showed that 1) All fingerprints appeared on the 10 papers after iodine test, performance were distinct and points of minutiae can be observed more than ninhydrin test. 2) Comparative detection of fingerprints on paper with different blood concentrations by Paired - Sample T-test at normal pork blood ,1:5, 1:10 and 1: 100, with the presence of different latent fingerprint by statistically significant at the .05 level. Appropriate paper in efficiency latent fingerprint on various types of paper by iodine and ninhydrin test on the nature of the porous surface, thin paper and lightweight paper can be observed the appearance of latent fingerprints more than porous surface, thick paper and heavyweight paper. Recommendations from the study indicate that iodine screening is a good method to detect fingerprints on blood-stained paper. Evaporate and Inhalation of iodine is slightly harmless. Inhalation of iodine for breath in long time can cause to be toxin and cancer. Ninhydrin test is not suitable for paper with blood stains. Suggestions should be made to determine the duration of fingerprints from blood stains and other types of paper, such as paper photo or plastic, such as water bottles, plastic bags and finding other chemicals that will help prolong of latent fingerprints.

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