Cogon: The C.S.I.



fingerprint colors
Colored fingerprint (Illustration by ECCP)

Imperata cylindrica, commonly known as Cogon Grass, apparently has a crime fighting application.

The cost-effective way—although not the only way—of assisting the investigator in proving a suspect’s connection to the crime is through the identification of fingerprints.  Although some fingerprints can be visible (such as bloody prints also categorized as patent prints) or plastic prints (e.g, imprints left on soft surfaces such as clay or wax), most prints in a crime scene are latent prints.  The latent prints are invisible, left by the oil and sweat secretions on the friction ridges of the finger.  The surfaces of the crime scene are dusted with the fingerprint powder to reveal these unique identifying patterns.

The most common fingerprint powders are black and carbon-based, however, the development of colored powders have given rise to clearer results due to the contrast the color makes to its surrounding surface.

Many fingerprinting powder for latent prints are hazardous to health, such as: lead powder, titanium oxide powder, Sudan III, Phloxine B, etc.  Hence, the search for a less toxic and less expensive fingerprint powder has led Malaysian scientists to find natural ingredients such as from Curcuma longa (Turmeric) in 2011 and recently using acid-modified Cogon Grass.

The dried Cogon is ground to a fine powder size between 1 – 50 μm the ample powder size that enables it to stick to the fingerprint sweat and oils on the touched surface; acid-modified (to interact better with the finger moisture); and applied on to writing paper, glass, metal and plastic surfaces with fingermarks from 1, 7 and 14 days.  Part of the experiment also submerged plastic and metal surfaces with fingerprints for up to 72 hours before the latent fingerprints were developed using the acid-modified Imperata cylindrica.

Imperata cylindrica powder was found to develop the prints from each test including those submerged in water for 3 days.  However, though potential is present more exploration needed to be done.  Particularly on making the powder size smaller to make the powder more sensitive to finger secretions.

The next time you see Cogon Grass, remember that much potential discoveries await this crime-fighting, grass-next-door!


W.Z.Low,etal.,Applicationofacid-modified Imperata cylindrical powderforlatent fingerprintdevelopment,Sci.Justice(2015)
Garg, K, et al., A New Technique For Visualization of Latent Fingerprint On Various Surfaces Using Powder From Turmeric : A Rhizomatous Herbaceous Plant (Curcuma longa), Egyptian Journal of Forensic Sciences (2011), 1, 53-57.

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