JPH0329642A - Potential finger print detecting method - Google Patents

Abstract

PURPOSE:To detect the image of a finger print in a simple manner without deterioration and/or decomposition of a substrate by bringing the potential finger print left on a subject in contact with a nascent ruthenium tetroxide gas in the potential finger print detection for the criminal investigation. CONSTITUTION:Sheets of filter paper are impregnated is respective ruthenium chloride solvent and cerium nitrate ammonium solution separately, and they are dried thereafter. When used, they are put into a small container in mutually over-lapped relation so that ruthenium tetroxide gas is produced with water added. Then the small container is gripped by a hand so that ruthenium tetroxide gas is thereby spouted out of a polyethylene tube 3 furnished with a check valve 4. Then, it is brought into contact with the potential finger print left on a substrate (subject) while it is changed into a black compound of ruthenium dioxide so that the potential finger print is thereby actualized. By this constitution, the finger print can thereby be detected very sensitively in a simple and safe manner at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a latent fingerprint detection method. When an oxidizing agent is reacted with an acidic aqueous solution of soluble ruthenium salts, ruthenium is oxidized and a gas of ruthenium tetroxide is generated.

When this gas comes into contact with oil and other organic substances in the latent fingerprints impressed on glass, wood, plastic, paper, etc., it reacts and is reduced to form a black compound of ruthenium dioxide, which makes a clear visible fingerprint. becomes. Although the latent fingerprint specimen is immersed in the liquid mixture, the same results can be obtained by spraying the I8 liquid.

Also, latent fingerprints can be detected in the same manner as described above using an aqueous solution or an organic solvent solution of ruthenium tetroxide prepared in advance.

There are generally three types of latent fingerprint detection methods: solid method, liquid method, and gas method, and this method falls under the gas method.

Known methods for detecting latent fingerprints using gas methods include the iodine sublimation gas method, the cyanoacrylate vaporization gas method, and the cyanoacrylate gasification method, which is currently patent pending.

In the iodine sublimation gas method, oil (human fat) in the fingerprint absorbs iodine gas from an iodine gas generator, and the resulting fingerprint image is photographed and used as evidence at the scene. In this case, the fingerprint image is due to the color of iodine absorbed in the oil.
Since it is a pale yellowish brown color, it is difficult to tell, so there is a method that has been put into practical use and improved upon by reacting penzoflavone, etc. with this oil-absorbing iodine to create an inclusion compound and detect a black-purple fingerprint image. , paper 5 is used as a specimen for this method.
It decomposes and disappears within a few days, limited to surfaces such as walls, and it is impossible to expose latent fingerprints on thermal paper because an organic solvent is used.

Next, the cyanoacrylate gas method is limited to the water and oil components of human secretions in fingerprints (it does not react with protein amino acids), and monomolecules polymerize when in contact with these components, resulting in a white fingerprint. However, this gas has a strong pungent odor and if used in large quantities, it will interfere with operation, and even if it is detected, it will adhere to areas other than fingerprints, making it unlikely that a clear fingerprint image can be obtained. However, the range of use is limited because it causes inconvenience in post-detection processing, and only smooth surfaces such as glass and plastic can be used as specimens. The smic acid method is extremely expensive, the sample is limited to paper, and it is highly toxic, so it has not been put to practical use.

Compared to these three gas methods, this method detects human secretions,
Proteins other than water and salt (change into amino acids)
Organic substances such as fat and epidermal cells react with volatile ruthenium tetroxide and are reduced, and black oxide of ruthenium dioxide is deposited on these organic substances. When generated, this acts as a catalyst and ruthenium dioxide is generated on top of it at an accelerated rate, making it possible to detect extremely clear fingerprint images of latent fingerprints deposited in small amounts on any specimen surface.

In addition, in order to make this black substance colorless, it is sufficient to oxidize it using an oxidizing agent and volatilize it as ruthenium tetroxide, and it is possible to restore the object without damaging it. Therefore, if this black substance is no longer needed, it will disappear immediately by wiping it with an oxidizing agent solution, and it will not contaminate or alter the quality of the specimen.

Claims (1)

[Claims] A method for detecting latent fingerprints, which comprises bringing a latent fingerprint impressed on a substrate into contact with ruthenium tetroxide to make it visible.