Main evidence types
The identification and analysis of body fluids (eg blood, semen, saliva or various body tissue)
- identification of the presence and extent of blood staining at scenes, on weapons, clothing and other items by visual and presumptive chemical testing
- identification of semen at scenes, on intimate body swabs, clothing and other items by presumptive chemical and microscopic techniques
- identification of saliva by presumptive chemical testing on clothing and other items
- identification of other body fluids and tissue by combination of chemical testing and microscopic techniques
- DNA profiling by DNA17 is the main means of comparison of body fluids. Access is also available for mitochondrial, Y STR and specialised DNA analytical techniques
- recognition and interpretation of blood pattern distributions both at scenes and on items in the laboratory
- identification and comparison of textile fibres and hairs
- recovery of trace fibre/hair from clothing and other items
- high magnification comparison microscopy with UV fluorescence of question fibres and hairs
- instrumental and chemical fibre comparison by a variety of testing, including microspectrophotometry, FTIR and TLC
Other biological materials can be recovered and identified, or referred to specialists or research institutes.
The examinations are often done in conjunction with other evidence types, such as fingerprint or shoe mark examination, and care is taken to identify protocols which maximise the evidential potential from all examinations.
Interpreting biological evidence
Since DNA and textile fibres are such widely occurring materials, and show a high degree of specificity, even at minute quantities, they can present a vast range of opportunities and challenges in progressing an investigation.
It is vital that information derived from such powerful evidence should be set in the context of the circumstances of the incident and interpreted with other findings appropriately. It is the role of the biology reporting officer to evaluate these findings within the context of the case either to advance the investigation or to present it as evidence in a court of law.