Tag Archives: forensics

The CSI Effect

Via BoingBoing, The Economist investigates the “CSI Effect” – the phenomenon whereby facts, falsehoods and mythinformation about criminal forensics procedures in entertainment media is hampering (and sometimes aiding) the detection and prosecution of real criminals.

… a new phrase has entered the criminological lexicon: the “CSI effect” after shows such as “CSI: Crime Scene Investigation”. In 2008 Monica Robbers, an American criminologist, defined it as “the phenomenon in which jurors hold unrealistic expectations of forensic evidence and investigation techniques, and have an increased interest in the discipline of forensic science.”


The most obvious symptom of the CSI effect is that jurors think they have a thorough understanding of science they have seen presented on television, when they do not. Mr Durnal cites one case of jurors in a murder trial who, having noticed that a bloody coat introduced as evidence had not been tested for DNA, brought this fact to the judge’s attention. Since the defendant had admitted being present at the murder scene, such tests would have thrown no light on the identity of the true culprit. The judge observed that, thanks to television, jurors knew what DNA tests could do, but not when it was appropriate to use them.

This sort of informational feedback loop happens in all sorts of places. I’m immediately reminded of the most common denigration of open-source software, namely that because anyone can download the code, anyone can work out how to compromise it. Of course, very few people do so… and proprietary software certainly isn’t immne from hacking, despite its closed nature. But is that because there’s less profit to be made from hacking Linux systems, as Microsoft advocates often suggest? Given the number of servers that run on *nix, I can’t believe it’s as clear-cut as all that.

But back to the forensics issue: the ‘open code’ of forensic science is helping some of the smarter criminals cover their tracks:

Criminals watch television too, and there is evidence they are also changing their behaviour. Most of the techniques used in crime shows are, after all, at least grounded in truth. Bleach, which destroys DNA, is now more likely to be used by murderers to cover their tracks. The wearing of gloves is more common, as is the taping shut—rather than the DNA-laden licking—of envelopes. Investigators comb crime scenes ever more finely for new kinds of evidence, which is creating problems with the tracking and storage of evidence, so that even as the criminals leave fewer traces of themselves behind, a backlog of cold-case evidence is building up.

Is there anything to be gained from trying to stem the flow of forensics knowledge out into the wider world? And if there is, how would one go about enforcing it?

Recycled plastics make crims harder to catch

heaps of plastic for recyclingThe increasing prevalence of recycled plastics in the manufacturing industry – doubtless due in part to the currently-struggling Chinese trash-trawling industry – means that a lot of everyday objects are now made from what you might call “mongrel plastics”, a blend of different chemicals with similar physical properties. Which is good news… unless you’re a detective who needs to lift fingerprints from the stuff, that is.

The recycled products may look similar, but the physical and chemical properties differ so widely from the plastics they replace that the techniques honed over recent decades to lift fingerprints off plastics are no longer effective, he says.

Traditionally plastics were made from just one or two chemical building blocks, arranged in a predictable structure. But even plastics with just a trace of recycled feedstock become much more complex. Although consumers are encouraged to separate their plastics for recycling, the resulting plastics are inevitably more of a mongrel product than the pedigree plastics they replace.

Now there’s a nice little rogue state niche industry waiting to be exploited – custom mongrel plastics that defy forensics efforts. The cost of hiring an out-of-work plastics geek would be offset by the higher prices you could charge to your secretive customers. [image by meaduva]

Fingerprinting mercury emissions from coal

About 2000 tons of mercury from human-generated sources enter the environment every year, but tracing natural versus human sources, and sorting out local pollutants from distant sources, has been been a problem. University of Michigan scientists say they’ve taken a big step towards reading mercury “fingerprints.”

“For some time, we weren’t sure that it was going to be technically possible, but now we’ve cracked that nut and have shown significant differences not only between mercury from coal and, say, metallic forms of mercury that are used in industry, but also between different coal deposits,” [ecologist Joel] Blum said.

How it works:

The fingerprinting technique relies on a natural phenomenon called isotopic fractionation, in which different isotopes (atoms with different numbers of neutrons) of mercury react to form new compounds at slightly different rates. In one type of isotopic fractionation, mass-dependent fractionation, the differing rates depend on the masses of the isotopes. In mass-independent fractionation, the behavior of the isotopes depends not on their absolute masses but on whether their masses are odd or even. Combining mass-dependent and mass-independent isotope signals, the researchers created a powerful fingerprinting tool.

[Image: Christopher Gruver]

Pollen-coated bullets to identify shooters

45mm ammunitionResearchers over here in the UK are working on a way to make it easier to identify criminals using guns. Their solution? Using pollen and tiny granules of crystal, you attach a unique “nano-tag” to every cartridge – sort of like a bio-chemical barcode.

The nanotags are made from pollen, and a mix of grains of crystal oxides such as zirconia, silica and titanium oxide. Using varying combinations of crystal and pollen grains, it is possible to make large numbers of unique tags.

“We decided to work with pollens because they have a unique structure, resistant to temperature and easily recognisable,” said Paul Sermon from the University of Surrey, who has led the research. “It’s also easily dispersed and carried around in clothes, skin, etc.”

But what if the criminal in question has obtained the rounds by criminal means, leaving no record to tie them to the bullets?

In addition to the tags, the researchers are working on a way to have gun cartridges retain skin cells from anyone that handle them, for later DNA-based forensic analysis. Micro-scale grit can effectively trap cells and protect DNA from the heat of firing. Today, cartridges are smooth and rarely retain DNA or fingerprints.

Well, OK. It’s very near-future sf-nal, but there’s still one glaringly obvious major flaw with this idea – it only has a chance of catching people who buy (or steal) their cartridges from new and legitimate stock, and who leave the spent shells for the police to find.

If there’s already a black economy where guns can be converted, hacked and (in some cases) built from scratch, I can’t see them struggling to adapt to reloading old cartridges. My father used to do that with shotgun rounds back in the eighties, and it’s a simple enough procedure that even a kid in their teens could pick it up.

So all a wide implementation of this idea would actually achieve would be to drive ammunition manufacture underground, adding a new (and lucrative) industry to the black economy. Because, y’know, the black economy just isn’t busy and powerful enough already. The problem with technology: when you’ve got a hammer, everything looks like a nail. [image by mx5tx]