Detection of Latent Fingerprints on Fruits and Vegetables

Research performed in May & June of 2006 By Gagan deep Singh , G.S. Sodhi,

and O.P. Jasuja

Hypothesis• Latent fingerprints are an important and

common piece of evidence at crime scenes. These prints may be present on various surfaces and objects, including the surfaces of fruits and vegetables. The study was conducted to determine the best procedure for developing latent fingerprints on fruits and vegetables.

What was used in this study?

• four fruits (apple, guava, banana, orange)

• three vegetables (tomato, onion, potato)

Samples of these fruits and vegetables were collected in fresh form from a retail market.

• Fingerprints were impressed onto the fruits in the same manner that a criminal would hold them. Prior to making the impression, the hands were subjected to typical day-to-day actions, which included the touching of the fingers to the face.

• Once the prints were put on the fruit, they were developed on the same day and at later dates which include days 2, 3, and 7. The fruits and vegetables that had been impressed were kept uncovered in a room to imitate actual crime scene conditions. The temperature during the experiment varied from 15 to 25 °C, with approximately 60% relative humidity.

There were two ways the prints were developed on the fruits and vegetables:

• Powder Method - Two types of powders were used: activated charcoal powder and lightning gray powder and were applied with feather brushes. After the development of the latent fingerprints, the excess powder was removed with a gentle blow of air. “Powdering is the most commonly used technique for smooth nonporous surfaces.” This technique is simple and inexpensive and provides instantaneous results that are ready to be "lifted”

• Iodine Fuming Method - Samples were exposed to iodine vapors by hanging in a glass chamber. The exposure time was determined by a visual assessment of the fingerprints. Iodine fuming is one of the oldest known techniques for the development of latent fingerprints.

Recording of Fingerprints

• The developed prints (powdered and iodine) were then lifted by clear adhesive tape, affixed to a clean white sheet of paper, and scanned using a flat bed scanner. • The results were recorded on

table #1

Conclusion• It was concluded that the apple

had the best surface for the development of latent fingerprints. This was because not only did the apple respond well to the grey powder but responded even better to the black.

• “The iodine fuming method provided prints that were clear in some areas, but the developed prints were not of good contrast in comparison to the ones developed with the powder.”

Conclusion cont.• The prints from the banana were the

same quality as the apple but once the banana started to age (the 3rd day) the bananas soft nature and moisture-containing surface smudged the prints. Lifting the prints became very difficult.

• The guava started to shrink, as time passed making it not as strong of a test subject. Gray powder worked best though.

• The uneven surface of the orange posed a problem.

• The tomato had a very smooth and glossy surface and because of its color, had a nice contrast to the black powder. Black powder proved to be a suitable method while iodine fuming did not.

In what ways will this research be helpful to the forensic science community or the courtroom?

• Using the powder and iodine fuming method in addition to MALDI-MSI, a powerful technology normally used to map different molecules within tissue sections, produces multiple images of fingerprints. This technology can also tell what a criminal ate and drank before they committed a crime. The equipment can detect certain food and drink, such as garlic and coffee. So if the criminal happened to eat something and leave it at the crime scene, the technique previously discussed and this technology could be used together to gain more evidence on a suspect.