IT'S being dubbed "molecular photofitting": producing an image of a suspect's face from DNA left at the crime scene. New research suggests that such reconstructions may soon be possible, giving police another investigative tool (see "Genetic mugshot recreates faces from nothing but DNA").
Until now, DNA has been used to predict only a few physical characteristics, such as certain shades of hair colour, and to draw broad conclusions about genetic ancestry. Concerns have been raised about these predictions being used for crude profiling, potentially racially tinged, which have led Germany and several US states to bar their use by police.
The new technique considers individual variation in facial structure, and thus promises greater refinement. But it could still be used in unsettling ways.
DNA-based forensics carry huge weight in the criminal justice system, and computer-generated images can be seductive. It is easy to see how a judge might accept sophisticated-looking 3D images computed from DNA as "probable cause" to issue a search warrant. Imagine being hauled off for questioning by the police, or having your home turned over by investigators, just because you resemble a photofit assembled from crime-scene DNA.
A conventional DNA test should put innocents in the clear – but only after unsettling scrutiny. That's why it is crucial for the accuracy of this approach to be validated independently before it comes into widespread use.
DNA-based analysis holds enormous power to convict and to exonerate. But as a two-part New Scientist investigation showed in 2010, its conclusions can be biased both by the statistical methods used and by subjective judgments (14 and 21 August 2010, p8).
The new tool wouldn't be used to convict, but wrongful arrests and unjustified searches are still violations of civil liberties. We shouldn't be blinded by awe at its power: justice won't always be done just because the face fits.
This article appeared in print under the headline "The new face of justice"
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