The effectiveness of an immunoassay test kit when blood is exposed to potentially degradative substances

HemaTrace� testing is performed on blood samples collected from crime scenes to determine the presence of human blood by forming antigen-antibody complexes with haemoglobin. This is vital to forensic investigations to ensure appropriate evidence is analysed to avoid wasting time and resources. However, false negatives have been found in casework and research, establishing questions regarding the effectiveness of the immunoassay test. This study aimed to investigate the effectiveness of HemaTrace� test kits when blood is exposed to potentially degradative substances. The substances were chosen for their potential casework relevance ? common household cleaning products for when there has been an attempted clean-up of a crime scene, vehicular fluids for hit and run or other vehicle involved investigations, and soil burials for cases where blood evidence has been buried, such as on clothed bodies. Each test of experiments varied in exposure period from 1 hour to 6 weeks based on realistic casework timelines to determine whether the length of exposure to the substances contributes to degradation. DNA and chemical analysis were also performe for further analysis of blood degradation. This study found that all the samples for which blood was exposed to the cleaning products and vehicular fluids for the designated time periods did not reduce the effectiveness of HemaTrace� test kits and did not impact on the quality or quantity of DNA extracted from the samples to the extent that the forensic usefulness was compromised. This study also concludes that bloodstains exposed to burial in soil for 3 weeks or more limits the accuracy and effectiveness of HemaTrace� test kits. These findings indicate that soil burials for 1 week or more do have a degradative effect on DNA, with a considerable impact on the ability to obtain forensically useable DNA profiles for routine and non-routine searching, as well as the capacity to use the profile for exclusionary purposes. Chemical analysis of samples found that mass spectrometry could be an effective way to assist in determining the presence of blood in a samples using a blood biomarker at m/z 557.17 as a degradation indicator.