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Abstract: Bloody exhibits, which are frequently encountered at crime scenes, commonly undergo latent fingerprint and biological examinations. These exhibits are routinely processed for fingerprint detection by using amido black, which is a protein dye. In this study, the OBTI kit was evaluated on amido black treated blood stains and fingerprints, and its sensitivity was compared to Kastle-Meyer (KM) testing. It was found that OBTI is a powerful confirmatory test for human blood that can be employed after amido black treatment. Its sensitivity equals or surpasses the KM test. The time interval between the amido black staining and the OBTI test is also critical.
Introduction
Bloodstained evidence is commonly encountered in crime scenes and may require latent fingerprint and biological examinations. In some cases, presumptive testing for blood cannot be conducted prior to fingerprint processing (e.g., when a fingerprint is made in blood or when the blood itself cannot be visually detected). In such cases, the fingerprint development process may involve the use of amido black, a dye that stains protein present in blood to give a blue-black product [1]. The Kastle-- Meyer (KM) color test [2] can be performed following amido black staining to give a strong indication for blood. However, KM is not specific for human blood [2]. In addition, further DNA recovery from amido black treated prints is not always successful, mainly from faint stains [3].
As mentioned earlier in part I, the Hexagon OBTI test [4] is a powerful and robust tool as a confirmatory test for human blood [5, 6]. It has been implemented in the Division of Identification and Forensic Sciences (DIFS) of the Israel National Police as a routine method along with the KM test.
As a part of the implementation process, the performance of the Hexagon OBTI kit was evaluated on amido black treated blood stains and fingerprints. Two operational formulations of amido black were evaluated in this study. The OBTI sensitivity was also compared with the routine KM test.
Material and Methods
Bloodstains
Whole blood samples in ethylenediaminetetraacetic acid (EDTA) from six individuals were serially diluted from 1:50 to 1:3200 with sterile water. Aliquots of 25 gl from each diluted blood concentration were applied as spots on glass slides and dried at...