The distribution and significance of amylase-containing stains on clothing

Assessing the background levels of body fluids on hands

Forensic scientists are often asked to assist the court by evaluating the significance of finding body fluids on the hands of an individual; however, there is an absence of published data regarding the background levels of body fluids on hands. Whilst the scientist can use casework experience to inform the courts on the significance of the results, it would be advantageous to have data which could assist with this interpretation. This study was designed to ascertain the background levels of blood, semen, saliva, hairs/fibres and staining/debris on hands in the general population by sampling from delegates attending a scientific conference. The findings suggest that approximately one third of the population would be expected to have hairs or fibres on their hands and that females are more likely to have visible staining on their hands than males. Presumptive tests for blood and semen yielded negative results in all samples; however, almost 2 % of the samples were found to contain a very low number of sperm heads. In contrast, the majority of samples tested positive for the presence of saliva using the presumptive Phadebas® amylase test. The data supports the caution applied by forensic practitioners when evaluating the presence of saliva detected using the presumptive Phadebas® amylase test based on the lack of specificity and indicates that the RSID™-Saliva test would be more suitable to use.

The validation of short tandem repeat (STR) loci for use in forensic casework

A quadruplex reaction has been developed which amplifies the short tandem repeat (STR) loci HUM-VWA31/A, HUMTHO1, HUMF13A1 and HUMFES/FPS. Detection of the PCR products employs denaturing polyacrylamide gels coupled with fluorescent-based technology. This system has been evaluated for use in routine forensic casework and has been shown to be both robust and reproducible. The quadruplex reaction is as sensitive as the commercially available HLA DQ alpha Amplitype typing system and can be used on both degraded and aged material. The problems of environmental contamination have been shown to be limited provided strict procedural practices are followed-i.e. physical separation of sample extraction and amplified products; the use of dedicated equipment such as pipettes; the separation of amplification preparation area. The ability of the system to detect mixtures and the successful analysis of case stains has shown that this system is well suited as a tool for forensic investigation.