PBS’s Tom Busey on the science behind crime scene investigation
By Lana Ruck- We’ve all seen it on a TV crime series – fingerprints taken from a crime scene are put into a computer, instantaneously matched to a person of interest, and voila! The crime is solved. As with many aspects of TV crime drama, however, fingerprint analysis is more complicated in real life. The reason? As PBS professor Tom Busey explains, human experts, not computers, actually do much of the work.
Busey, whose research generally relates to visual perception, has been working with crime scene analysts since the early 2000’s. His lab explores such topics as how fingerprint analysts become experts and how they differ from novices; what visual features of fingerprints are useful for identification; and how incomplete information and noise – like partial or smudged prints – affect analysis. Many of us know that fingerprints are unique to each person, but as Busey explains, each and every print we leave is unique as well, depending on how wet or dry our hand is, what material we’re touching, and other factors.
Considering this extraordinary variation, much of Busey’s research relates to the problems that fingerprint analysts face in determining whether two fingerprints are from the same person. For despite their rigorous training, which typically takes two years, fingerprint analysts have a much harder job than we often acknowledge. Insofar as an error can send an innocent person to jail, or let a guilty person go free, the stakes of fingerprint analysis are quite high. Analysts must be cautious when matching samples and rate prints as inconclusive more often than not. This too, however, can have its downside.
The trade-off between “false alarms” and “misses” depends on a key question: How willing are we, as a society, to implicate an innocent person in order to catch a guilty one? The Busey Lab is currently working to understand how the public views this trade-off, so as to clarify this issue for officials. (You can participate directly in this work by completing the survey found here.)
Ultimately, however, the Busey Lab hopes that their observations may one day contribute to the making of deep-learning computer algorithms that can perform fingerprint analysis, taking some of the pressure off human experts in ambiguous or high profile cases. To this end they are working with expert fingerprint analysts to identify the most useful features for matching prints.
Undergraduate researchers in the Busey Lab are currently branching out to another aspect of crime scene investigation: blood pattern analysis. This involves mixing, dipping, and even sipping and coughing fake blood to mimic common blood patterns found at crime scenes. In addition to presenting their work at conferences, a few of these undergraduate lab members have recently completed the Cadet Officer Program, a training program for IU students who wish to pursue future careers in law enforcement.
As the Busey Lab shows us, the study of human visual perception has broad social relevance. It has direct application to solving crime and improving the systems of criminal justice.