Rapid Blood-Traces Fixing at Crime Scenes with Heat

Sarena Wiesner, DIFS, Israel Police, Jerusalem, Israel (sarena_wiesner@police.gov.il)
Ziv Grimberg, DIFS, Israel Police, Jerusalem, Israel

Blood-contaminated fingerprints are significant evidence for forensic investigators in high profile cases, providing a direct link between the suspect and the crime. Blood enhancement techniques are operationally used to recover maximal ridge detail. The standard protein dye-staining procedure includes a chemical blood-fixing step, which requires an initial, prolonged drying period, for natural coagulation to occur. Occasionally, it is crucial to complete the development process shortly after the crime was committed. This study explored, the use of heat as an alternative method to the standard chemical fixing of fresh bloody marks. First, blood-contaminated fingerprints were deposited on different types of surfaces (car parts, glass, and flooring tiles), and heated for different periods, prior to development by Amido Black solution. The results showed that heat was successful in fixing blood, while the required temperature and heating durations were inversely proportional.

This observation was in correlation with theoretical heat-transfer data, calculated by the Lumped Heat Capacity model, also demonstrating the impact of the thermal time constant of each surface, on the conditions required for the full fixing of blood.

A portable, and tailor-made heating device was developed for the use in crime scenes, allowing to shorten the necessary fixing process from hours to minutes. For Next, depletion footprints and shoeprints were deposited with fresh blood on floor tiles. the quality of the marks developed with Amido Black after fixing with heat was compared to that of marks fixed with 5-sulphosalicylic acid.

Examination of the first marks with heavily contaminated blood showed that the blood which was fixed with 5-sulphosalicylic acid solution was diffused, whereas the heated marks at the same areas where properly fixed and thus a high resolution detailed image was achieved. The fifth marks which naturally were much fainter prior to development, developed in high quality with both fixing methods.

Short Biography of Presenting Author

Sarena received her B.Sc. in Chemical Engineering, from The Technion, Israel in 1993 and her M.Sc. in Chemistry, from Casali Institute in the Hebrew University of Jerusalem in 2003. Her Thesis Topic was "Mass production of Indanedione and advancing the operational use of the reagent".

She enlisted to the Fingerprint Development Laboratory in the Forensic Department of the Israeli Police force in 1994. She was a member of the International Fingerprint Research Group. In 2002 she transferred to the Toolmarks and materials Laboratory, and was certified as expert in shoeprint and tiremark comparison. In 2017 she was nominated head of the questioned Documents Lab and in 2021 returned to the Fingerprint Development Lab as Head of the Lab.

Mrs. Wiesner has given numerous presentations concerning fingerprints, shoeprint and Questioned Documents in meetings in Europe and the US, and published numerous papers about topics in these areas.

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