Iodine Fuming for latent fingerprints

Iodine Fuming

At crime scene the development of latent fingerprint are done by two methods

Physical methods

Chemical methods.

One of the chemical method for development are - 

Iodine fuming -

Iodine fuming is a very old but effective method. It is very convenient to use. 

Inexpensive and non-destructive(stains are temporary)

Fast and cheap.

The process of iodine fuming is done by two methods, in both the principal 

is same but processing is different. First one is a lab process -

In a lab process iodine fuming is done inside a chamber. First step is to set 

up the fuming chamber and place the iodine crystals . Iodine crystals are sublime 

at room temperature ( directly change from solid to gas ) and you can also 

place hot water into the chamber. You can use a paper clip and a stiff

wire to suspend the specimen into the chamber. Wait for 5 to 10 minutes the

 iodine crystals filled the chamber with violet vapors. Check the specimen. 

The brown (yellowish brown) color fingerprints were developed on the specimen. 

( Iodine fumes are absorbed by the fat and oil deposits of the latent 

fingerprints ). Fingerprint are not permanent and the developed fingerprints 

should be immediately photographed. For fixation of fingerprints , starch is used

 that give the fingerprint a blue-black color and fix it for weeks to months. 

Permanent fixation is done by using benzoflavone and it darkens the print.

For field use(in mobile crime team) iodine fuming kits were given to experts. 

In iodine fuming kit a glass tube , iodine crystals , blowing tube , filtering wool ,

 calcium carbonate granules (drierite is used in some kits) is present . 

First we place wool then calcium carbonate then again wool then Iodine crystals and again wool one

by one.(some forensic companies provide partially pre-assembled set with rubber stoppers on both

sides). Next step is to blow (by vinyl tube or in some by rubber pump) the tube from one side to

warm the iodine crystals. Iodine crystals release the vapors which fumed to the targeted print from

other end of tube. Make a distance of one inch between the tube end and the target area. Grab the

tube tightly so some heat of hand also transferred to the tube.(some modern versions use battery

power for heat and some has disposable iodine fuming guns). 

Safety points - stains on skin and clothes occurred due to iodine fuming . Iodine is toxic and

irritating and strongly corrosive. Always wear gloves and take necessary precautions like goggles ,

protecting clothing. Perform the experiment near window or under exhaust fan.

This technique used on both non porous and porous surfaces .

Iodine fuming work great on fresh prints(few days).

Iodine fuming is done before ninhydrin treatment. 

Iodine fuming mostly used on papers  , raw wood , leather etc.

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About forensic fingerprint

MR. DEEPAK PAWAR has been working as Finger Print Expert / Police Officer in Finger Print Bureau , Delhi Police at New Delhi since 2001 . He is the senior most Finger Print Expert , attending / visited several scene of crime and solved many crime cases .He has passed M.Sc (Chemistry) and he is the Member of International Association of Identification . He is the Member of Delhi Police welfare association . He is supervising the Forensic , New Delhi District , Mobile Crime Team . He is one of the Expert in the Special Investigation Team held for investigation of important cases . He has been giving fingerprint proficient training to Delhi Police personnel's . He has been Presented / giving lectures on topics related to forensic science . He is also making examination paper of Finger Print proficient course . He is awarded with Police Medal by MHA and Delhi Police.

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