How to Lift Fingerprints: Cyanoacrylate (Super Glue) Fuming

This project explains the science behind the cyanoacrylate fuming process and how it is used for latent fingermark detection. Cyanoacrylate super glue reacts with the traces of amino acids, fatty acids, and proteins in the latent fingerprint and the moisture in the air to produce a visible, white polycyanoacrylate that forms along the ridges of the fingerprint. This reaction takes place faster when the cyanoacrylate is heated inside of a chamber with some water inside to provide humidity. Fingerprint powders can potentially contaminate the evidence and ruin the opportunity to perform other techniques that could turn up a hidden print or additional information. Therefore, investigators may examine the area with an alternate light source or perform cyanoacrylate (superglue) fuming before using powders.

Latent prints are not readily visible to the naked eye and must be developed in some way to increase their visibility and contrast. The method shown in this post is to physically enhance the latent prints by using a homemade cyanoacrylate fuming chamber. The fuming chamber can be made fairly easily or be substituted with a glass aquarium or clear plastic container.

Supplies

- Super Glue: https://amzn.to/3xfBxdE

- Aluminum Weighing Dish: https://amzn.to/3Lz6eTh

- Zephyr Brush: https://amzn.to/3qbbr9z

- Lightning Powder: https://amzn.to/3qbbr9z

- Ultra Clear Tape: https://amzn.to/3qbbr9z

- Fingerprint Cards: https://amzn.to/3qbbr9z

Step 1: Video

This video shows the entire process that is outlined below.

Step 2: Introduction:

- Cyanoacrylate superglue fuming is a chemical method for the detection of latent fingerprints on non-porous surfaces such as plastic, glass, rubber, and varnished wood.

- This method works by the deposition of polymerized cyanoacrylate ester on residues of latent fingerprints.

- It can be used to develop and detect clear, stable, white-colored fingerprints. Cyanoacrylate fuming is a non-destructive way to develop latent fingerprints, where the prints can be lifted multiple times.

- It can be useful when lifting prints from delicate items or when the prints can not be lifted using traditional means.

- Around the same time in the late 1970s, forensic scientists in the UK, Canada, and Japan all independently discovered that superglue could be used for latent fingerprint development.

- Fingerprints are a valuable piece of evidence because of their uniqueness and can be found on the objects present at a crime scene.

- They can be used to identify the suspect or link them to a crime scene and an object or weapon.

Step 3: How It Works

- Fingerprints are formed by sweat released from pores present on the friction ridge skin of hands and fingers.

- When the finger touches any surface, the sweat from the pores on the ridges gets deposited in the form of contours which creates an impression of the ridge pattern.

- Since sweat is colorless the fingers leave a colorless impression that are called latent fingerprints.

- Cyanoacrylate adhesives are monomeric adhesives and generally set quickly to clear, hard glassy resins.

- Polymers of alkyl 2-cyanoacrylate are also known as superglues.

- Alkyl 2-cyanoacrylate is an acrylate ester which has the triple-bonded carbon-nitrogen (cyano or nitrile) group bonded within an ester.

- It forms vapors when heated in a sealed chamber which interacts with certain eccrine components of latent fingermark residues.

- The acrylate vapors get polymerized on the deposited proteins from the latent print and form into white, stable, and clear print outlines.

- This hard, white polymer is known as polycyanoacrylate.

Step 4: The Fuming Chamber

- A simple homemade fuming chamber like this can be used to develop cyanoacrylate vapors with a mug warmer

- This one is made from a plastic base, thick copper wires, and a clear plastic bag.

- Something like this can be made fairly easily or even a glass aquarium or clear plastic container can be used as a fuming chamber.

- Objects to be processed are suspended in a chamber and a small amount of liquid cyanoacrylate is heated to around 80 to 100°C to produce sufficient vapor.

- The heating of cyanoacrylate reduces the time required to develop latent fingerprints.

- Overheating of cyanoacrylate ester should be avoided as it produces toxic hydrogen cyanide if heated above approximately 220°C.

- A container of water can be placed in the chamber to provide sufficient humidity for the development of the prints.

- This is because low humidity causes the appearance of weakly developed prints with poor contrast.

- The development process should be regularly inspected to avoid over-development.

- Commercial fuming chambers will often have features such as temperature control, proper vapor circulation, humidity control, and automatic removal of the cyanoacrylate vapor.

Step 5: Developing the Prints

- Cyanoacrylate fumes are an eye and respiratory tract irritant so it is important to take all of the necessary safety precautions and have proper ventilation.

- Latent fingerprints can be developed on non-porous surfaces with the following steps:

- Place the object with the latent fingermark into the fuming chamber with its surface being exposed.

- Add an aluminum dish onto the warming plate in the chamber and add a few drops of liquid cyanoacrylate into the dish. - When the chamber is sealed, plug in the warming plate to start the process.

- Allow the items to be exposed to the fumes until whitish-colored fingerprint patterns appear.

- You can add a fingermark to the inside of the chamber to give you a good indicator of when the prints are done developing.

- The cyanoacrylate-developed prints may be used as is or further enhanced by dusting with regular or magnetic fingerprint powder and/or staining procedures.

- This is to help the prints stand out better for easier and more reliable identification.