Why particles matter to forensic scientists

If you have any questions, please see the Help Section or contact us. As people move throughout a scene, dust and other particulate matter can be transferred from the respective footwear or other objects to various surfaces that have been walked upon.

Electrostatic dust print lifting devices give the scientist the ability to enhance, collect and preserve such impressions. Electrostatic dust print lifting devices operate by charging a plastic film, placed over the dust print, which creates electrostatic adhesions and draws the film onto the surface bearing the print.

The dust particles are attracted to the film because of this charge and adhere to it. The film retains a charge after the unit is turned off, thus retaining the particles of dust. The print must be composed of loose residue, and the residue must be dry for this process to work. Also, a proper ground must be achieved when applying the electrical charge. On some surfaces it is difficult or impossible to achieve a ground and the procedure will not work, necessitating alternative lifting methods.

The top image shows one type of electrostatic dust print lifter in use. It is on a conductive surface, requiring the use of a grounding plate held off the surface with a nonconductive sheet while applying a charge to the silver-backed lifting media. Below is a footwear impression on a metal surface left and the resultant lift photograph enhanced. Note that the lift is a mirror image of the actual impression. Media Center.

Contact DPS. It looks like your browser does not have JavaScript enabled. Please turn on JavaScript and try again. Forensic Science Services. On this basis, the jury delivered a guilty verdict. When we started exploring and carrying out some experiments on these particles we discovered that they were in fact not rare, but abundant.

And they lasted a long time on clothing — many hours rather than minutes. The significance of these particles in that case was completely changed by a series of experiments. These appear against the backdrop of the warnings given about the impact of budget cuts on the justice system and on the quality of forensic science.

Of the reasons cited as to why evidence was misleading in those cases, nearly a third of the reasons were identified as misinterpreted forensic science evidence. The technological capabilities to measure and classify trace materials have increased, and the accuracy of the measurements that can be made is greater than ever before. When we find trace evidence, such as explosive residue particulates or a trace DNA profile, at a crime scene or on a suspect, we can often provide good indications about what it is or who it came from.

But there are big questions that still need to be answered for us to be able to know what that trace evidence means and how significant it is for a case. There is more on this in my TED talk. Studies carried out in the US and the UK have illustrated the cases where evidence was misinterpreted, which have resulted in exonerations. But these are only the cases where the misinterpretation was identified and the appeal case was successful.

The cases that have been identified so far are simply the tip of the iceberg. The significant cuts across all the sectors that have a bearing on the justice system have meant that the research that is needed to answer these questions is not being prioritised and funded.

But just as the breath-taking scale and complexity of icebergs and the oceans are being realised as the To do that we need to harness the best scientific approaches and enable high quality research within the professional and academic science communities.