News & Views

Washing out the stains

Can washing remove semen stains?

Locating semen stains on clothing usually relies initially on a chemical screening test followed by a microscopic examination for spermatozoa (sperm cells) to confirm the presence of semen. But are the tests used sensitive enough to detect semen after an item has been washed?

The term ‘washed’ can mean many different things ranging from a quick rinse, a full wash cycle in a washing machine or soaking and then washing for example.  How long the item is immersed in water, the type of detergent and temperature used will have some effect on whether semen can be detected afterwards. A scientist will need to be given as much information as possible about the type of washing used so that they can advise on the likelihood of detecting any staining and decide what tests and strategy they should employ.  This is also relevant when an expert is asked to comment on whether stains are likely to be found on a washed item, and whether the laboratory testing was appropriate. 

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DNA transfer through non-intimate contact

Male and Female symbols

In sexual offence cases where no semen is detected, the presence of female DNA on penile swabs and underwear of the defendant may be put forward to address the issue of whether or not sexual intercourse took place.  However it is known that DNA can be transferred through non-intimate contact so research was commissioned to investigate the frequency and amount of DNA which might be transferred in this way.  The work was recently published in Science and Justice by the UK and Ireland Association of Forensic Science Providers’ Body Fluid Forum which our expert Julie Allard co-chaired at the time of the research.
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Streamlined Forensic Reporting – the hidden truth

Forensic EvidenceStreamlined Forensic Reporting (SFR) was rolled out nationally in April 2013.  The CPS guidance document states that  “SFR is a revised case management procedure for producing forensic evidence at court, which seeks to reduce unnecessary costs, and delay in the criminal justice system. The process takes a more proportionate approach to forensic evidence through the early preparation of a short report that details the key forensic evidence the prosecution intend to rely upon.  The aim is to achieve early agreement with the defence on forensic issues but where this cannot be achieved in the first instance, to identify the contested issues.”

The first stage SFR1 report is not a witness statement or report to which the Criminal Procedure Rules apply.  It is, at this stage, difficult for the defence to determine whether they dispute the evidence being provided as the information that the SFR1 provides is often nothing more than a bland description of the analytical result, with little if any background or interpretational information.  READ MORE

A Forensic Market in Flux

Looking down the microsocpe

Over three and a half years on from the closure of the Forensic Science Service, and you might be forgiven for thinking that the market for forensic services would have settled down.  However, it would appear that things are as changeable as ever as budget cuts bite, the money spent on forensic science shrinks further and the long promised government strategy for forensic science has yet to be published.READ MORE

Demonstrating that penetration has occurred when no semen is found: the whys and wherefores of Y-STRs

DNA

Evidence to demonstrate that penile or digital penetration of the vagina has taken place can be difficult to find in some cases.  Traditional DNA profiling techniques can’t really help as the few male cells potentially deposited are overwhelmed by the large amount of female DNA present in the vaginal cells.  Y-STR typing is a form of DNA analysis that targets just the DNA present on the male Y chromosome allowing production of a male Y-STR profile even in the presence of seemingly overwhelming amounts of female DNA.READ MORE