Inherent Fluorescence
Definition
The luminescent signal from latent print residue itself under ALS illumination, without any development agent; primarily from sebaceous components such as squalene and fatty acid derivatives; examined as the first step before any treatment.
- Field
- Latent print development
- Trigger
- ALS illumination, no reagent applied
- Source
- Squalene and other sebaceous fatty acid derivatives
- Sequence
- Examined before cyanoacrylate fuming or dye staining
Common questions
Why check for inherent fluorescence before applying any development chemical?+
Any print that already fluoresces can be photographed non-destructively at that stage. Applying a chemical reagent first risks masking or altering that natural signal, so examiners image it before committing the surface to a treatment step.
Does inherent fluorescence work on every latent print?+
No. Squalene degrades with time and environmental exposure, so older or weathered prints often show weak or no inherent fluorescence, which is why it is treated as a first look rather than a reliable stand-alone method.
Related terms
- 1:1 Macro Photography
- Photography at a reproduction ratio of 1:1 (image sensor size equals subject size); the mandatory standard for all latent fingerprint photography before...
- Alternate Light Source (ALS)
- A device emitting light at selected wavelengths (typically 415 to 535 nm) used to detect biological fluids that fluoresce or absorb light...
- Ardrox
- A commercial fluorescent dye mixture (originally for aircraft-skin crack detection) that fluoresces broadly under 365 nm UV illumination; used as a post-CA...
- Barrier Filter
- An optical long-pass filter placed over the camera lens and worn as goggles by the examiner during ALS examination; blocks the excitation...
- Basic Yellow 40 (BY40)
- A fluorescent dye (excitation 450-490 nm, emission ~530 nm) applied immediately after CA fuming with a simple aqueous rinse to remove excess;...
- Cyanoacrylate (CA) Fuming
- The development of latent prints on non-porous surfaces by exposing the item to ethyl or methyl cyanoacrylate vapour in a humidity-controlled environment;...
- Ethyl Cyanoacrylate (ECA)
- The active monomer in forensic CA fuming products and most consumer Super Glue formulations; undergoes anionic polymerisation initiated by nucleophiles (water, amines)...
- Lumicyano
- A proprietary Foster + Freeman formulation that combines a fluorescent CA monomer with standard CA developer, enabling simultaneous development and fluorescent marking...
- Rhodamine 6G
- A fluorescent dye applied as a post-treatment to cyanoacrylate-developed fingerprints; excited at 530 nm (green), it emits at 565-590 nm (yellow-orange), greatly...