Ninhydrin
Definition
A chemical reagent (2,2-dihydroxyindane-1,3-dione) that reacts with alpha-amino acids in latent print residue to produce a purple-blue compound (Ruhemann's Purple); the primary development method for porous surfaces worldwide.
- Chemical formula
- 2,2-dihydroxyindane-1,3-dione
- Reacts with
- Amino acids in latent print residue
- Color produced
- Purple-blue (Ruhemann's Purple)
- Best for
- Porous surfaces like paper and cardboard
Common questions
What does ninhydrin actually do to a latent fingerprint?+
Ninhydrin reacts with amino acids left behind in the latent print residue. This chemical reaction produces a distinctive purple-blue compound called Ruhemann's Purple, which makes the fingerprint visible for photography and comparison.
What surfaces work best with ninhydrin?+
Ninhydrin is the standard development method for porous surfaces worldwide. It works particularly well on paper, cardboard, and other absorptive materials where latent prints soak into the surface.
Why is the resulting color called Ruhemann's Purple?+
The purple-blue compound produced when ninhydrin reacts with amino acids in latent residue is named after its chemical structure and discovery history. The color itself is the visual result of that specific chemical reaction and is distinctive enough for forensic identification.
Related terms
- ACE-V
- Analysis, Comparison, Evaluation, Verification: the four-stage method for latent print examination used by accredited forensic fingerprint laboratories. Analysis examines the latent in...
- AFIS / NAFIS
- Automated Fingerprint Identification System. NAFIS is the NCRB-operated national instance running on the Idemia Morpho engine, integrated with CCTNS under ICJS.
- Alpha-Amino Acids
- Molecules bearing an amine group on the carbon adjacent to the carboxyl group; the primary molecular target of ninhydrin, DFO, and indanedione...
- Cyanoacrylate Fuming
- A fingerprint development technique in which ethyl cyanoacrylate vapour polymerises onto eccrine sweat residue on a latent print, producing a stable, white...
- DFO (1,8-Diazafluoren-9-One)
- A fluorescent ninhydrin analogue used for latent fingerprint development on porous surfaces; excite at 450-470 nm (with secondary absorption extending into the...
- HFE (Hydrofluoroether)
- A class of solvents used as carriers for ninhydrin, DFO, and indanedione formulations; lower toxicity and flammability than older acetone or ethanol...
- Indanedione-Zinc
- A fluorescent amino acid reagent (indane-1,3-dione complexed with zinc chloride) that produces an orange-yellow fluorescent product; reported to be more sensitive than...
- Latent Print
- An invisible or barely visible impression of friction ridge skin deposited on a surface by eccrine sweat and sebum, requiring a development...
- Minutiae
- Level 2 ridge characteristics (ridge endings, bifurcations, dots, islands, lakes, spurs, crossovers). The primary individuating features used by AFIS algorithms and human...
- Patent Print
- A visible fingerprint left in a coloured medium (blood, ink, paint, dust, grease). Photographed in situ; usually no chemical development needed.
- Physical Developer (PD)
- A multi-bath silver-deposition wet-chemistry method that deposits silver metal onto fatty latent print residue on porous surfaces; the only technique that recovers...
- Plastic Print
- A three-dimensional impression in a soft material such as putty, soap, candle wax, wet paint or chocolate. Recorded by photography and silicone...
Explained in these topics
- Chemical Methods: Ninhydrin, DFO, Indanedione and VMDA chemical reagent (2,2-dihydroxyindane-1,3-dione) that reacts with alpha-amino acids in latent print residue to produce a purple-blue compound (Ruhemann's Pur...
- Fingerprint Development, Lifting and AFIS ComparisonReagent that reacts with amino acids in latent residue to give Ruhemann's purple. Standard development reagent for porous surfaces such as paper and cardboard.