DNA profiling from blood traces present on clothing’s and detected by Benzidine test in forensic cases

Abstract

In many instances, several types of evidences are recovered in distinct forms or contaminated with any other types of valuable evidences. For forensic investigation purpose, all these evidences have their potential values and often provide link between the victim and accused/suspect. In case of murder, sexual assault or hit and run cases, a few blood drops are frequently recovered from the scene of occurrence. The forensic biologist helps the investigation agencies in the collection of the evidences from the spot of incidence and analysis of the same in the laboratory. Police submit the evidential samples in the Forensic laboratory with a query of DNA analysis, for cases like murder, attempt to murder, rape, concealment of identity of individual/fragmented body parts or where body is transferred after murder from one place to another. In outdoor crimes such as rape/ sexual assault, biological materials transfer from victim to accused/ culprit or vice versa and to the surroundings.1 The place of offence must be fixed by the investigation agencies.2 Therefore, traces of blood droplets found at crime scene should be processed for DNA profiling. But due to the traced quantity, such samples get consumed in presumptive blood tests, such as Benzidine test and usually not considered for DNA analysis. In few cases where the blood is washed off from the crime scene/surface, it becomes one of the most crucial problems faced in forensic examination of the criminal cases to detect the blood spot. The surfaces are examined for the presence of blood (a necessity) by use of benzidine or phenolphthalein test. The crucial facet is faced when the blood samples are transferred on clothes in very less quantity. Then, it can be directly tested with benzidine that is competent enough to generate complete DNA profiles. BENZIDINE is a greyish-yellow to greyish -red, crystalline solid. It is toxic by ingestion, inhalation, and skin absorption. Combustion produces toxic oxides of nitrogen. Benzidine molecular weight 184.242g/mol, an aromatic diamine widely used in industrial processes, that’s why, it is used to prepare other chemicals at few instances, it is used for biological analysis. It is also a powerful carcinogen in many animal species. Some presumptive tests have been described for blood stains recognition,3 one of the most commonly used tests is Benzidine and its derivative Tetramethylbenzidine (TMB).4 It has been observed that the administration of benzidine has been shown to produce tumours in liver, hamster liver, and other tissues of exposed animals.5 In most cases to ingestion or inhalation of benzidine workers in the industry suffered a tremendously increased risk of bladder cancer.6 Many investigators have studied the mutagenicity of benzidine and their substitute in short-term tests such as the Ames test.