ABSTRACT: Biological stains can be difficult to detect at crime scenes or on items recovered from crime scenes. The use of a versatile light source may assist in their detection. The ability of Polilight® to locate potential semen, saliva, and blood stains on a range of substrates and at different dilutions was tested. We also tested the use of Polilight® in comparison with conventional chemical-based presumptive screening tests such as acid phosphatase (AP), Phadebas®, and luminol, often used in casework for detecting potential semen, saliva, and blood stains, respectively. The Polilight® was able to locate stains that were not apparent to the naked eye. The color of the material on which a stain is deposited can have an effect on the detectibility of the stain. The Polilight® was found to be comparable with the AP and Phadebas® tests in terms of its sensitivity. In a comparative study between the AP test and Polilight® on 40 casework exhibits, one false-negative result was observed when using the Polilight®. On a series of mock casework exhibits it was determined that the Polilight® can be used successfully to locate saliva stains for DNA analysis. The sensitivity of luminol for detecting potential bloodstains was greater than that of Polilight®; however the Polilight® has particular application in instances where a bloodstain may have been concealed with paint. Overall, the Polilight® is a relatively safe, simple, noninvasive, and nondestructive technique suitable for use in forensic casework.
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