Ninhydrin and its New Forensic Usege as Humen Fluid Detector

On Mero, Division of identification and forensic science , Israel police , Tel-Aviv, Israel (onmero@gmail.com)

Saliva and sperm are body fluids containing personally, unique, genetic information through
DNA molecules enabling the identification of a person with statistical confidence. dry samples of these fluids are sometimes overlooked due to their transparent/white nature and their relatively small stain size, its detection is difficult and hence sampling and administering it as evidence is challenging. In addition, existing methods of identification such as UV light for sperm identification often give a "false positive" detection, and in other cases the reaction is hidden due to the background and the staind material properties.
This study examined the potential of a known fingerprint development agent as a saliva and sperm development agent. Ninhydrin compound, which is currently used as a Fingerprint development agent on porous and absorbent surfaces, is known for its color changing binding reaction to amino acids through the Ruhemann reaction, and is a familiar substance used by crime scene investigators.
Ninhydrin compound reacts with the free NH2 group in amino acids and proteins and
since body fluids as sliva and sperm, contain proteins, it should supposedly react with ninhydrin' thus identified through the purple color appearance.
Experiments testing the ninhydrin compound ability to react with these body fluids, to form significant color reaction (without special means) was examined, as well as the use of this method on several types of absorbent and non-absorbent surfaces with different surface properties.
Samples were taken from the target platforms and a genetic profile was obtained from these samples.
Results from this research have shown that these body fluids residues were colored by the ninhydrin compound in a very distinct color tone and furthermore, it did not affect the ability to obtain a full genetic profile from the samples.