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Biology, blood patterns + DNA

Biological samples are amongst the most commonly collected from items associated with crime and from crime scenes.

Our consultants have expertise in biology, body fluids, DNA and blood pattern analysis and have many years experience of interpreting DNA profiles from different items and body fluids. This includes expertise in STR, Y-STR and Low Copy Number (LCN) analyses. LCN DNA is a technique of DNA analysis that attempts to amplify and identify extremely small quantities of DNA. LCN DNA is one type of a loose group known as low template DNA analysis techniques. These techniques are often used for ‘touch DNA” where an individual has made contact with a given item.

Interpretation of standard DNA results or Low Copy Number DNA results can be challenging; results are often said to be incomplete (partial) and/or mixtures of DNA from more than one person. In many cases it is not possible to attribute any LCN DNA result obtained to a specific body fluid due to the very low levels of DNA being analysed. However, newer techniques are being applied (e.g. mRNA) to samples and we can assist with understanding the importance or otherwise of the results.

Correct interpretation and ensuring adequate checks are very important to ensure that the analytical scientist has presented the DNA evidence and findings correctly. Opinion can be provided regarding possible mechanisms of DNA transfer, whether direct or indirect (“secondary transfer”).

Blood pattern analysis (BPA or blood spatter) relates to the appearance of a blood stain on a surface. Patterns or distribution of groups of blood stains can assist in reconstructing the activity at a scene, including whether they were caused by actual contact or were caused as a result of being airborne.

Our consultants are highly experienced in blood pattern analysis and have reported many BPA cases relating to crime scenes and items of clothing to address specific allegations about a sequence of events – such as whether an individual was involved in an incident or was an innocent bystander.

In sexual assault cases, the result of the DSAC examination and the contents of the Medical Examination Kit can provide significant information that needs to be considered in the overal context of the case. Our experts are vastly experienced in interpretation of findings including transfer and persistence issues, lubricants and condoms.

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