Crime and Punishment and Science: What Exactly is Scientific in Forensics?

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(Image credit:  http://newsroom.ucla.edu/stories/q-a-with-jennifer-mnookin:-raising-the-bar-for-scientific-evidence-in-court)

Systematic discrimination in the criminal justice system has been painfully highlighted recently in mainstream media.  As a scientist, researcher, and person of color, I have been thinking about ways to eradicate that discrimination in both long and short times scales.  Based on my experience trying to change safety culture (i.e., helping researchers incorporate safety into their research as a necessary component), I have learned the hard way that change on this scale does not happen quickly.  Thus, as much as I want things to change right now, we really need are short-term solutions, and legislative and systematic changes to change the system in the long term.

One short-term solution may very well lie within scientists’ reach.  An opinion piece in the Washington Post titled, “A wake-up call on the junk science infesting our courtrooms,” made me remember a session at a scientific conference that I went to recently.  For readers not in technical fields, one way that scientists disseminate their research findings is to present them at conferences to other scientists from all over the world.  As a microscopist, I recently attended the Microscopy and Microanalysis Meeting, which brought together scientists who work with all forms of microscopy (a device that magnifies objects and gives information about the materials that make up that object by capturing how light, electrons (essentially electricity), or a sharp probe interact with that object).  Another advantage of going to conferences as a student is being able to attend sessions discussing topics I would not normally think about.  The one I thought of while reading the opinion piece was titled “Microscopy and Analysis in Forensic Science.”  One of the talks I listened to discussed how long gunpowder generally stayed on the person of someone who fired a firearm and how likely (note the use of the word likely) it was that someone could have gunpowder on their person even if they did not fire a weapon with gunpowder.  During this presentation, I was surprised by how much people in forensic science dealt with probability and then chilled by how much rode on the accuracy and reliability of their observations and, in some cases, calculations.

So what exactly is lumped under the term “science” in courtrooms?  The most famous and, perhaps, most accurate science currently in courtrooms to determine guilt and innocence is DNA testing.  DNA is a collection of proteins that make up genes.  DNA holds all the information to make up an individual, and part of it is unique to each person (unless that person has an identical twin), which is why scientists can use it to identify someone.  Even DNA testing, however, has limitations.  While determining that DNA samples do not match is fairly simple, reliably determining that two samples are indeed from the same person is much more difficult; scientists must test multiple places along the DNA to determine how closely the samples match.  The more places, the more definitive the test, but also the more expensive!

Other scientific methods used in courtrooms to determine innocence and guilt are not so reliable.  The opinion piece names several other forensic methods – “bite mark analysis, firearms identification, footwear analysis and microscopic hair comparisons – [which] lack adequate scientific validation.”  Two studies – a report by the President’s Council of Advisors on Science and Technology (PCAST) and a study by the Innocence Project and FBI – found that most of the forensic evidence from these types of methods just was not true.  For instance, a staggering 95% of the testimony by people who examined hair was flawed.

The report by the PCAST puts forth a solution that makes sense; methods should be tested in conditions like those found in everyday life using the scientific method and only be allowed into the courtroom if they are found to be accurate and reliable.  Methods that have been found to be limited should be presented as such.

Something this article drove home for me is that everyone should play a role in eliminating systematic discrimination, but, like our DNA, we each have a role to play.  Some will make their voices heard by going to protests.  Others, like me, will use their scientific training to make mostly objective methods to unravel a crime and to identify guilt and innocence.  But as scientists, we also know that every method has its limitations, and those limitations should be made clear in courtrooms as much as their merits.  Thus, a short-term solution that scientists uniquely can help to develop is refining forensic methods to be more accurate.  No person on trial deserves less.

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