Locating, Developing and Preserving Fingerprints Flashcards
How did you locate these fingerprints?
These fingerprints were located in the Christchurch Forensic Laboratory using various chemical methods, and with the assistance of the Poli-light, which is a specialised torch which emits high intensity light in a range of different wavelengths, or colours, of light.
The fingerprints were then photographed, and then forwarded to the South Island Forensic Fingerprint Section for further examination.
How do you decide on which method to use when developing fingerprints on a particular exhibit?
When selecting a method to develop fingerprints on a particular exhibit we assess several factors, however the primary factor is the porosity of the exhibit (or how absorbent the exhibit is).
We use different methods for developing fingerprints on porous exhibits, such as those made of paper or cardboard, as opposed to non-porous exhibits, such as those made of plastic or glass.
For example, tin foil would generally be treated for fingerprints using superglue fuming, because it is classed as a non-porous type of exhibit, whereas a paper note would generally be treated with a chemical called indanedione, because it is classed as a porous type of exhibit.
What is superglue fuming?
Superglue fuming is a method used in the fingerprint lab for developing fingerprints on exhibits. The exhibit is placed inside of a sealed chamber along with a small amount of glue. When heated, the glue forms a vapour which fills that chamber and adheres to the fingerprint residue, making any fingerprints on the exhibit more visible.
Fingerprints that have been developed with superglue fuming may be enhanced when viewed under UV light. The superglue deposit which is attached to the fingerprint residue, reflects the UV light, therefore providing greater contrast between the fingerprint and the background.
What is panacryl?
Panacryl is a chemical that is used for developing fingerprints on exhibits in the fingerprint lab. The chemical is applied to a surface by either spraying the exhibit, or submerging the exhibit in the chemical solution.
The panacryl reacts with fingerprint residue, and glows bright green when viewed under the Poli-light. This increases the contrast between the fingerprint and the background surface, making it easier to locate and photograph any fingerprints.
What is indanedione/ninhydrin?
Indanedione and ninhydrin are chemical methods for developing fingerprints on porous items such as those made of paper or cardboard.
The exhibit is submerged in the chemical solution, and then allowed to dry. The chemical reacts with the fingerprint residue which has absorbed into the paper, and stains the fingerprint therefore making it more visible.
What is a poli-light?
We use a specialised torch, called a poli-light, to assist us in locating and photographing fingerprints both at the crime scene, and in the fingerprint lab. The poli-light emits light in a range of different colours, or wavelengths, of light, which is either reflected or absorbed by the fingerprint, depending on the type of residue, or the chemical used to enhance the fingerprint. This makes it easier to locate and photograph fingerprints
For example, fingerprints that have been treated with a dye stain called panacryl glow bright green when exposed to blue light, and viewed with a yellow colour filter attached to the camera.
