The Limits of Science

On Wednesday, February 10, George Perrot was released from prison, after spending thirty years behind bars for raping a woman in 1985.  In all that time, Perrot, and the woman he was accused of raping, have maintained his innocence.  On Wednesday, an appeals judge finally agreed, and set Perrot free, stating that:

“The record before the court, which I have subjected to rigorous examination, makes me reasonably sure that George Perrot did not commit those grave offenses.”

The judge also recommended that prosecutors not seek to retry Perrot for a third time.

The interest that I have in this case is not based on Perrot’s innocence – I’ve had no knowledge or interest in this case before hearing about it on NPR Thursday.  What I am interested in, however, is the reason that Perrot was released after all this time, and why the judge is so certain that Perrot is innocent.

That reason is science.  (Not specifically physics in this case, but at the end of the day, most science comes back to physics, doesn’t it?)

Perrot was convicted, twice, based largely on FBI hair analysis.  This was before more modern DNA analysis was available – in 1985, hair analysis was done by hand with a microscope.  In a stunning admission earlier this year, the FBI and the Justice Department “formally acknowledged that nearly every examiner in an elite FBI forensic unit gave flawed testimony in almost all trials in which they offered evidence against criminal defendants over more than a two-decade period before 2000.”  When they say almost all, they mean it. Of 268 cases reviewed, “26 [examiners] overstated forensic matches in ways that favored prosecutors in more than 95 percent.”


Now of course, not all of those 95% of cases relied solely on the hair match evidence.  But some did.  Like George Perrot’s.

Florence Graves of the Schuster Institute for Investigative Journalism summed the problem up nicely in an NPR article:

“Many people in the scientific community knew decades ago, including the FBI, that hair microscopy was used beyond the limits of science.”

Beyond the limits of science.  That’s a really interesting concept in and of itself.  What are the limits of science?  Science, is after all, the pursuit of truth, the pursuit of understanding how the universe works, and how we can make it work for us.  However, science isn’t perfect.  Science doesn’t have all the answers, and can’t explain everything.  Science is based on questions, and every new discovery leads to new questions, or a complete overturning of the answers to the questions that came before.  We understand more than we ever have, but we might also know more things that we don’t know than we ever have.

The problem we run into is when we let the hubris of our knowledge drive us to pretend that we know more than we really do.  Say, for example, in reporting hair matches with more accuracy than the science is actually capable of.  Or assigning causation when the evidence merely suggests a correlation.  Science allows us to make incredible discoveries and change our lives and the world around us, but it is not infallible.  Science is not all knowing, even if outside pressures (like political pressure to secure a conviction, for example.  Or monetary pressure from oil companies to ignore climate change) want it to be.  The limits of science are not actually limits of science – they’re limits to how we apply the science that we have access to.  Science is fallible because we are fallible, and because we want science to conform to our desires and expectations.


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