Tearing knickers and why it needs to be done

By Anna Sandiford 10/04/2012

Those leaders in science blogging and the founders of the the Ig Nobel Prize at improbable.com blogged last week about new research from Otago University with a blog entitled A new twist in forensic knicker-testing. It’s a brief (no pun actually intended) post that states an NZ study “tested the tearing of knickers, and found that meaningful results are not easy to obtain if one examines only the fabric itself.” The research itself was actually about lab testing completed in order to test the tear behaviour of three knit fabrics, typical of those used to manufacture knickers, including the effect of laundering (Dann et al 2012. Tearing of knicker fabrics. For Sci Int doi).

Whilst this may seem strange to some, it is in actual fact one of those areas of research on which papers have already been published. Sexual assaults are a very common source of complaints to police. They are also amongst some of the most difficult to assess, particularly if the parties are known to each other; it’s often a he-says-she-says situation. The way fabric is damaged is often a key part of a police investigation and can assist with determining the credibility or otherwise of the accounts of the (usually) male and female involved in the incident.  Clothing fabrics evolve over time so it is important for there to be continuing research as new fabrics come onto the market.

The research findings were not necessarily  surprising: cotton and cotton-rich fabrics were more difficult to tear than modal-rich fabrics; addition of elastane increased the time for the tear to start because elastane allowed the fabric to stretch more before breaking. The materials behaved differently depending on which direction they were torn; fabric that had been washed needed less force to cause tearing than new. Overall, when examining torn clothing items the fibre content and age of the garment should be taken into consideration. However, there were limitations to the testing, including that only fabric was tested, not actual items of underwear.

In fact, if I didn’t know the significance of this research then I would probably be muttering about how research money should be spent on things that we don’t already know; surely all this research is doing is stating the obvious – of course older more worn and washed knickers will tear more easily than new ones and of course some materials are easier to tear than others and of course if they have elastic in them then they’ll stretch more before breaking because that’s the whole point of adding elastic.

However, the American National Academy of Sciences gave forensic science a massive hammering in 2009 – basically, everything apart from DNA needed a thorough review before being considered acceptable in a court of law and that we should regularly test the science. They were right. Which means we have to carry on researching and then testing and updating the original research.

What it means now is that there is a whole raft of research going on that should have been done years ago, before any of this sort of information was given as evidence in court. In accordance with numerous Codes of Ethics, criminal procedure rules and forensic requirements, scientists should state the basis of any opinion they give in court, including citing relevant, peer-reviewed scientific literature.

This new research paper doesn’t mean that if damage is seen to underwear a sexual assault necessarily occurred – it just means forensic scientists can cite another scientific paper regarding the mechanisms of tearing. Whether a sexual assault occurred will be for the court to decide and more than just underwear damage is usually required to make that decision.