A stain with all the fixing’s – Enhancement of fingermarks in blood using a combined fixative and aqueous protein stain

• Published in: Forensic science international 2024-10, Vol.363, p.112181, Article 112181
• Main Authors: Elder, Bethany, Sharp, Morgaine, Harvey-Walker, Nicholas
• Format: Article
• Language: English
• Subjects: 5-sulfosalicylic acid; Acid Black 1; Acids; Amido Black 10B; Blood; Crime scene; Crime scenes; Ethanol; Fingerprint; Fingerprints; Fixing; Forensic toxicology; Methanol; Naphthalene black 12b; Proteins; Reagents; Staining; Stains; Stains & staining
• ISSN: 0379-0738; 1872-6283; 1872-6283
• DOI: 10.1016/j.forsciint.2024.112181

The use of protein stains to enhance fingermark ridge detail in blood is a common technique used by forensic practitioners around the world. Amido Black is one of the most favoured protein stains due to its strong staining ability. The most common formulation of Amido Black is methanol based, with an ability to simultaneously fix and stain the blood impression, however methanol is toxic and can disrupt some surfaces, potentially compromising fingermark detail. If the surface is suspected of being a material that is impacted by methanol, there is an alternative aqueous formulation, which requires a fixative step to set the blood prior to staining so as not to wash away potential ridge detail. The multi-step process of aqueous protein stains is tedious and numerous studies have been conducted to improve the formula to achieve a combined fixing/staining solution that performs like the methanolic reagent. A combined fixative and stain formulation of aqueous based Amido Black was compared to a multi-step formulation with a separate sulfosalicylic acid fixative. Of the 243 split fingermark impressions analysed the majority (63.5 %) showed no preference to either treatment, with a marginally greater proportion of the remaining marks slightly favouring the combined fixative and stain formulation. Given that the new combined formulation performed broadly similarly to the existing multi step formulation, the potential time savings of this simpler approach may be beneficial to implement into operational use. •We compared a combined and separate fixative/stain solution of aqueous Amido Black.•A combined fixative/stain solution for aqueous Amido Black is more efficient.•A combined fixative/stain solution for aqueous Amido Black develops better marks.•Sulfosalicylic Acid as a fixative does not have to be applied as a separate step.•Combining fixative and stain preserves and enhances blood fingermark ridge detail.