Basic Yellow 40 (BY40) is a fluorescent dye with an affinity for cyanoacrylate (superglue) residues. After fuming evidence with cyanoacrylate, BY40 reacts with those residues, causing them to glow under blue light with yellow goggles/filters. This fluorescence enhances the visibility of latent fingerprints, providing crucial detail. BY40 works particularly well on multicolored or patterned surfaces where traditional powders would be hard to apply and visualize.
Equipment
- Fuming Chamber (optional): A controlled environment for cyanoacrylate development, if not already performed.
- Dipping Tank or Tray: A container large enough to submerge the evidence item.
- Spray Bottle: Used for targeted BY40 application if a small area requires processing.
- Drying Station: A well-ventilated area to air-dry treated items.
- Forensic Light Source: Typically in the blue wavelength range (around 450 nm).
- Yellow Viewing Goggles: Filters out ambient light and highlights the BY40 fluorescence.
Materials and Chemicals for 1 Liter of BY40
- Basic Yellow 40 Dye: Typically 1-2 grams.
- Methanol: Approximately 1 liter.
- Graduated Cylinder: For accurate liquid measurement.
- Beaker or Measuring Flask: Used for mixing the solution.
Mixing Procedures for Basic Yellow 40
- Safety First: Wear gloves, eye protection, and a lab coat as methanol is flammable. Work in a well-ventilated area.
- Measure Methanol: Use a graduated cylinder and pour approximately 950 ml of methanol into the mixing beaker. Reserve some for adjusting the final volume.
- Dissolve BY40: Carefully weigh out 1 to 2 grams of Basic Yellow 40 dye and gradually add it to the methanol while stirring gently. Complete dissolution is crucial.
- Check Concentration: Observe the solution under a forensic light source and assess the fluorescence. If too weak, add a small amount of additional BY40.
- Adjust Volume: Using the reserved methanol, top the solution up to a final volume of 1 liter in the mixing beaker.
Processing Evidence with BY40
- Cyanoacrylate Fuming (if required): If latent prints have not yet been developed, cyanoacrylate fuming needs to be conducted first.
- BY40 Application:
- Dipping: Submerge the evidence in the BY40 solution for several seconds to a few minutes, monitoring fluorescence.
- Spraying: Mist the target area with a fine spray of BY40 until fluorescence is visible.
- Rinsing (optional): A gentle water rinse can remove excess BY40 (particularly if over-application obscures fingerprint detail).
- Drying: Allow the evidence to air-dry completely in a well-ventilated drying station.
- Examination: Use a forensic light source and yellow viewing goggles to examine the treated evidence for fluorescent latent prints.
Storage of Basic Yellow 40
- Light-Resistant Container: Use an opaque or amber bottle to protect the solution from light degradation.
- Cool, Dark Location: Store in a cool area away from direct sunlight and heat sources.
Shelf Life
A properly mixed and stored Basic Yellow 40 solution generally has a shelf life of roughly 6 months. However, it's best to regularly check its fluorescence strength under a forensic light source to ensure continued effectiveness.