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Environmental chemistry for the CSI generation

Wednesday, 19 August 2015 at 2:05:PM

Forensic science and the CSI effect

Forensic science is easy these days, isn’t it? Got a scraping of paint from a suspect’s car? Stick it into your analytical magic-machine, and you’ll know the make, model and year within what … 30 seconds?

If only the reality was actually like that! You probably don’t need me to tell you that shows such as CSI: Crime Scene Investigation are more than a little unrealistic about what forensic science can achieve. One manifestation of this so-called ‘CSI effect’ is that jurors have an over-simplified understanding of what forensic evidence can – or cannot – prove.

Bringing polluters to justice

Whether driven by the CSI effect or by other factors, there can be no doubt that the importance of analytical chemistry in forensic analysis is certainly increasing. Nowhere is this more apparent than in the world of environmental chemistry, where polluters are increasingly being brought to justice following work on linking the pollution back to a suspected source.

Evidence gained through these ‘environmental forensics’ investigations has helped to deliver guilty verdicts in a number of high-profile cases, with defendants hit with clean-up costs and legal fees running into millions of dollars.

Harnessing the potential of new analytical techniques

GC×GC, which separates complex mixtures into their individual components, effectively generates a ‘fingerprint’ for a particular sample, enabling it to be matched against suspect samples

In light of this, it might come as a surprise that data from one of the most powerful new analytical techniques in environmental forensics – two-dimensional gas chromatography (GC×GC) – has never actually been presented as evidence in an environmental pollution trial.

While at the International Network of Environmental Forensics (INEF) conference in Toronto earlier this month, I participated in a discussion that explored the reasons for this. A key factor is that no-one wants to take the risk of being the first to present GC×GC in court, when faced with the stringent Daubert criteria relating to the admissibility of scientific data.

At the meeting, the first steps on the road to resolving this problem were proposed by Dr Donald Patterson (Exponent, USA). The plan is to conduct a ‘round-robin’ study late in 2015, inviting GC×GC users around the globe to participate in a blind study to detect the amounts of hazardous chemicals called polycyclic aromatic hydrocarbons (PAHs) in a complex mixture such as diesel.​ If you're interested in participating in the study, just contact Donald Patterson ( and Jack Cochran (

Proving the value of GC×GC as evidence

The hope is that this study will allow analysts to gauge whether different instruments give the same results when presented with the same sample. Such reproducibility data will then be valuable in convincing the legal profession of the validity of GC×GC, and encouraging them to use it in court. It should also encourage more laboratories to invest in GC×GC – although many individuals are enthusiastic about the technique, the reality is that most laboratories still rely on older, less advanced technologies.

However, even with that achieved, a considerable challenge will remain – explaining to juries, barristers and judges why GC×GC provides a more compelling basis for a conviction than other techniques. Although the chromatograms themselves are easy enough to describe, I wouldn’t want to have to describe how GC×GC actually works. I had to do that for my Ph.D. viva, and it was nerve-wracking!

Laura McGregor

Laura McGregor gained her Ph.D. in Environmental Forensics from the University of Strathclyde, UK, where she used GC×GC–TOF MS to ‘chemically fingerprint’ environmental contaminants. Now Product Marketing Manager for Markes’ TOF MS products, in her free time she occasionally finds herself lamenting the depiction of forensic scientists in CSI: Crime Scene Investigation. ​


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