The Red Thumb Mark

By R. Austin Freeman

Originally published in 1907. Reprinted in 2002 by the House of Stratus, 214 pages, paperback, fiction

Review by Hans Sherrer

For Justice:Denied magazine

Red Thumb Mark

In A Printer Looks At Fingerprints (Justice:Denied, Vol. 2, No. 9), Fred Woodworth mentioned a book written in 1907 that cast doubt on the reliability of using fingerprints to identify the perpetrator of a crime. However, he didn’t know the title. My curiosity piqued, I did some sleuthing and was able to find the book he referred to. Imagine my surprise at finding that book, The Red Thumb Mark, is still in print 97 years after it was first published.

Reuben is guilty as sin! That was the police’s conclusion after Scotland Yard declared Reuben Hornby’s thumb-print was imprinted in blood on a paper found inside a safe burglarized of diamonds worth £30,000 (over $250,000 in 2004 dollars). The case against Reuben seemed airtight: The safe’s lock showed no signs of tampering, and only three people, including Reuben, had access to the safe.

Reuben’s lawyer was so convinced of the case against him that he recommended he “plead guilty and throw himself on the clemency of the court as a first offender.”

Yet if the damning evidence against him was true – why did Reuben loudly proclaim his innocence? That is the mystery that intrigued Dr. John Thorndyke enough for him to agree to investigate the case for Reuben’s defense. Dr. Thorndyke was a medical doctor and a lawyer who like his contemporary, Sherlock Holmes, used logic and deduction to solve seemingly insoluble problems.

Dr. Thorndyke began his investigation by approaching the situation from the perspective opposite of that taken by the police: Could the alleged incriminating fingerprint evidence actually prove Reuben’s innocence?

During conversations with Dr. Jervis, his young assistant, Dr. Thorndyke makes many perceptive observations about the law enforcement process and his approach to a criminal case that are as relevant today as when The Red Thumb Mark was written nearly a century ago. Three of those that are particularly notable are:

● “… the presumption of innocence is a pure fiction, the treatment of an accused man, from the moment of his arrest, is that of a criminal.”

● “But there is no such thing as a single fact that ‘affords evidence requiring no corroboration.’ As well might one expect to make, a syllogism with a single premise.” (Merriam-Webster’s 11th Collegiate Dictionary defines a syllogism as: 1 : a deductive scheme of a formal argument consisting of a major and a minor premise and a conclusion (as in “every virtue is laudable; kindness is a virtue; therefore kindness is laudable”).

● “Now the one fact which stands out and dominates the whole case is this: The prisoner’s connection with this case rests solely upon the police theory of the infallibility of fingerprints.”

The fruits of Dr. Thorndyke’s investigation into the evidence against Reuben became public knowledge at his trial. On the most obvious level the trial testimony provides an excellent primer on why fingerprint evidence is fallible, and how easily it can be forged. While on a deeper level it demonstrates how easy it is for police and prosecutors to use testimony related to a single supposed fact -- such as a fingerprint or DNA analysis, or an eyewitnesses recollection -- as the ‘magic bullet’ to make an accused person appear guilty. Thus a primary lesson to be learned from The Red Thumb Mark is that in the absence of corroborating evidence from disparate sources, a person’s possible guilt must automatically be doubted.

A sub-plot that provides a bit of levity is Dr. Jervis’ pining for Miss Juliet Gibson, a young woman he thinks is betrothed to Reuben, and who will marry him if he is acquitted. Dr. Jervis’ desire to not do anything that even appears to compromise the honor of Miss Gibson and himself is refreshingly quaint compared to what is considered acceptable behavior in this day and age.

Is Reuben acquitted, or were Dr. Thorndyke’s efforts for naught? Does Dr. Jervis get the fair maiden Miss Juliet? You’ll just have to read the book to find out. The Red Thumb Mark is a smashing good mystery, and although it has a lot of solid information, it is a quick read since it was written for the general public and not technical readers.

The Red Thumb Mark is available at many public libraries either from their collection or by interlibrary loan. The 2002 reprint published by the House of Stratus can be ordered from your local book store for $9.95. Or order with a credit card from Justice:Denied’s website by going to and clicking on The Red Thumb Mark.