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My Master’s Dissertation: Secondary Transfer of Trace DNA

Samuel H ATobias17 April 2016

One of the forefronts of forensic DNA research is the secondary transfer of trace DNA. Secondary transfer is an example of passive transfer and occurs when one person’s DNA is deposited onto an object by someone (or something) else. Trace DNA is usually found in small amounts from sources such as skin cells which are deposited on an object after it has been touched or casually handled.  If this object becomes evidence in a criminal investigation, the possibility of placing an innocent individual at the crime scene arises. The occurrence of secondary transfer of trace DNA has only come to light in the last several years and so there is currently not much known about it. The study I have proposed for my dissertation will evaluate if relative pressure of contact has any effect on the transfer of trace DNA. Knowing this will reveal what factors are required for secondary transfer to happen, and help uncover its relevance in a forensic context.

Tobias, Samuel

Me dusting for prints in a CSI practical session

Forensic DNA technology has progressed to the point where genetic profiles can be generated from samples where only a few cells are present. For this reason, steps have to be taken to prevent any contamination of the samples. The research undertaken by the UCL Centre for Forensic Science is carried out in the collaborative UCL division of Biosciences, UCL CFS and UCL Institute of Archaeology Ancient DNA facility. The ultra-clean lab provides a safe and contamination-free space to extract the DNA from the low-template samples of trace DNA.

As the use of DNA in forensic science continues to expand, the need for scientific literature on the subject will only grow as well. The occurrence of secondary DNA transfer is on the leading-edge of forensic biology research; therefore, my ultimate goal is to create a publishable study that will contribute to the field of forensic DNA research in a beneficial way.

Forensic Outreach With Inspire

MichaelaRegan19 August 2015

In May and June, Sherry, Sally, Nadine and I had the opportunity to provide three forensic outreach sessions to 3-5 year olds at three different schools in Hackney. All of us have had different experiences with outreach but none of us have worked with such a young age group, and we were aware that factors such as their attention spans and their vocabularies would affect how we delivered the sessions. We knew that we needed to make it simple but fun so that the children would stay interested, which is challenging when you are used to explaining your research to a more academic audience.

To start off, we briefly explained the process of investigating a crime (demonstrating the role of witnesses and searching for ‘clues’ to ‘catch the bad guy’) through different activities. We demonstrated the difficulty of being a witness by giving them an image to memorise for a minute and then asking what colours the different objects were. After which, we got them to try and link paw prints to different animals as a way of describing the theory behind footprints. To conclude, we wanted to find a memorable activity to inspire them so we used fluorescent powder to demonstrate the way trace evidence can transfer and persist; putting fluorescent powders on our hands and then shaking theirs. After we shook all their hands we turned off the lights and used a blue light to show them that even though evidence may be invisible to the naked eye, sometimes it can still be located.

UV light on hands

UV light on hands

I feel these activities were very successful with the children and that they were very enthusiastic and sometimes even amazed by them. I also found it thoroughly enjoyable and motivational – it was encouraging to see them so interested in forensic science and I hope that this encourages them to keep learning more about this subject area.