Saturday, May 3, 2025

Misleading Evidence - An Important Lesson

It's quite rational to believe that the more evidence a theory has, the more accurate it will be.  And that's probably the case normally.  But there was a wonderful exception to this in a Sherlock Holmes story called, "The Adventure of the Norwood Builder."

In this story, a man was arrested on suspicion of murder.  Lots of evidence pointed him to the crime.  Holmes for some reason wasn't convinced, even though he realized the evidence definitely seemed to confirm the suspect of the murder.  But eventually the police found evidence that seemed beyond dispute.  A bloody fingerprint exactly matching the suspect.

This should have been enough to close the case.  But Holmes instead realized this proved the innocence of the man with the fingerprint.  HOW?

Because Holmes examined the exact spot where the fingerprint was just the day before and KNEW it was not there during his initial examination.  This was while the suspect was already jailed for the suspicion of the murder.  There was no way the suspect could have broken out of jail - and he definitely wouldn't do it in order to place even more evidence against himself.  Holmes realized somebody else had the suspect's fingerprint and put it there.

Even with all these spoilers, I'm still leaving a lot of good stuff out of the story.  Holmes ended up solving the case and clearing the initial suspect.  The real criminal who framed him did it almost perfectly, except he made the one mistake of not knowing when to stop.  That was his undoing.  Otherwise, he would have beaten Holmes.  But he couldn't resist planting the fingerprint later on when he realized what great additional misleading evidence it would be.

So I learned an important lesson here.  Even a ton of evidence leading a certain direction isn't always correct in the direction it's leading.  One additional piece can change the whole course of an investigation.  In other words, sometimes even if you follow a whole lot of strong, available evidence, you can STILL reach the completely wrong conclusion.  


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