Evaluation of indirect transfer mechanisms of semen under varying test conditions.

There is limited data available on the subject of indirect transfer of non-visible body fluids, particularly semen, and often forensic science practitioner experience alone must be used to guide expectations. It can be difficult to assess the likelihood of proposed transfer scenarios without knowledge of how different variables can affect a transfer. The following work carried out by the Association of Forensic Service Providers UK and Ireland Body Fluid Forum explores how the features of transferred semen change with differences in the primary and secondary surface (porous and non- porous), different contact types (passive, pressure and pressure+) and with wet and dry primary stains.

Enzyme activity, DNA degradation and drying times of semen, saliva and vaginal material.

The stability of enzyme activity and the amount of detectable DNA within liquid samples of semen, saliva and vaginal material were tested across a number of days. The concentration of DNA within neat semen and saliva samples fell significantly after one week of refrigeration. No apparent change in acid phosphatase or amylase enzyme activity was observed in neat semen and saliva samples over 96 or 72 h respectively.

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.

Examining the transfer of male DNA onto female underwear in simulated non sexual social interaction versus digital penetration to assist in the evaluation of results in casework scenarios.

Experiments have been carried out by the UK and Ireland Association of Forensic Science Providers Body Fluid Forum (AFSP BFF) to determine the levels of male DNA, detected during Y-STR analysis, that may be expected on female underwear from non-sexual social interaction and digital penetration, versus non-sexual social interaction only. The data obtained strongly supports the existing assumptions made: whilst low levels of DNA may be inadvertently transferred to the inside surface of a female's underwear during social interaction with a male, there is a low expectation of detecting a matching Y-STR profile to that male, which is suitable for statistical evaluation, unless he is a co-habitant of that female.

Illuminating the benefits and limitations of forensic light sources.

Forensic light sources, such as a Crime-lite, are used in forensic laboratories and by police staff in the examination for, and detection of, biological material. Whilst the benefits of using forensic light sources are relatively well understood, their limitations are less-so. This report details the outcome of studies, validation and review by three forensic laboratories, as well as three case examples, to highlight both the strengths and weaknesses of the tested forensic light sources and to demonstrate that, whilst a useful preliminary screening tool, they should not be used in isolation without subsequent presumptive chemical testing.