Saturday, September 21, 2013

Mark Twain and Fingerprints: Part 1

“When I was a youth, I knew an old Frenchman who had been a prison-keeper for thirty years, and he told me that there was one thing about a person which never changed, from the cradle to the grave – the lines in the ball of the thumb; and he said that these lines were never exactly alike in the thumbs of any two human beings.”

— From “A Thumb-Print and What Came of It,” one of the stories serialized in Mark Twain’s Life on the Mississippi, published in 1883.

Today on Crime and Science Radio, during my interview with Leslie S. Klinger about Sherlock Holmes and forensic sciencewe briefly mentioned Mark Twain's use of fingerprints.  (You can listen to the show here:)

I wanted to expand on that mention of Twain, and it seems it will take more than one blog post to do it.  So here's Part 1!

Mark Twain (Samuel Langhorne Clemens) was one of the earliest writers to make use of fingerprints in a story.  If you mention this to his devoted readers, most will quickly say, “Yes!  In Puddin’head Wilson!”

I will get to Puddin’head Wilson a little later, but it is not the first work in which Twain uses the uniqueness of fingerprints as an element of the story’s plot.  That honor goes to “A Thumb-Print,” one of the stories in Life on the Mississippi. In it, a thumbprint leads to the identification of a murderer. For a number of reasons, Twain’s use of fingerprints in “A Thumb-Print” is remarkable. 

In 1883, as shown by the passage quoted above, Twain wrote that a thumbprint was unique to an individual, and did not change. 

These are two essential characteristics.

Solving crimes is in part a matter of identification of the individuals involved and the exclusion of individuals not involved:  These bones belong to this individual, they cannot be the bones of that individual.  This person was here, and not this personHere are the people who might have done this.  These are the people who could not have done this.  The  greater the degree to which a trait can be associated with one individual and no others, the stronger proof it offers as evidence.

Let's say there is a bank robbery.  Witnesses say the robber has long, red hair and was wearing dark clothing. 

Police know that millions of people have red hair and a good number of those may also own dark clothing.  A smaller percentage of those millions may have been able to be at the bank at that time, but this will still be a very large group. While the witnesses’ descriptions may be of help in immediately following a suspect from a scene, or prove valuable if the robber is caught some other way, they don't narrow the field much.

One other important element of determining identification is mutability.  Can this trait be changed, or appear to be changed?   In our example above, hair can be dyed and cut, clothing can be easily changed.  So again, the witnesses description quickly loses value.

“In these days, we photograph the new criminal, and hang his picture in the Rogue’s Gallery for future reference; but that Frenchman, in his day, used to take a print of the ball of a new prisoner’s thumb and put that away for future reference.  He always said that pictures were no good — future disguises could make them useless; ‘The thumb’s the only sure thing,’ said he; ‘you can’t disguise that.’ And he used to prove his theory too, on my friends and acquaintances; it always succeeded.” 
— from "A Thumb-Print and What Came of It."

Today we would ask, “Did the killer leave any DNA or fingerprints at the scene of the crime?”  Thanks to news stories, high profile cases, and television dramas about forensic science, we accept these forms of evidence, often without thinking much about them.

Most of us are aware that DNA was not discovered by scientists until the mid-20th century and wasn’t in use forensically until late in that century.  We know that the use of fingerprints has been around longer, but have little idea of the story of the development of their use to catch and convict criminals.  

At the time Twain wrote "A Thumb-Print," if you talked to the average person on the street and said that if a criminal touched something with an ungloved hand, he might leave a uniquely identifying mark that could lead to his conviction, you'd have probably been met with disbelief.  This would have sounded like voodoo to most of his contemporaries.  

When Mark Twain was born in 1835, fingerprints were unknown in the western world as a means of catching criminals.  Although a treatise on the potential for using them in this way written in about 200 B.C. in China, and we know that fingerprints were used as signatures in Babylon dating back to 1792-1750 B.C., by the early 19th century these were forgotten lore in most of the world.  During most of Twain’s lifetime, there was no system in place anywhere for the scientific, forensic use of fingerprints. 

Until very late in the 19th century, even those who were studying scientific approaches to catching criminals were largely unaware of the potential of fingerprints, and no system of classification of fingerprints had been established in law enforcement organizations.

The first scientific treatise on the subject to be written in English and to become widely known was not published until 1892 — Sir Francis Galton’s Finger Prints.

1892.  Nine years after the publication of “A Thumb-Print.”

How did Twain know?  
More on the history of the forensic use of fingerprints. 
And links for those who want to know more.

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