Consider a recent example: On Feb. 17, 2004, Texas executed Cameron Todd Willingham for the arson deaths of his three daughters. In September, an investigative article in The New Yorker revealed that Mr. Willingham was innocent. It sparked a series of investigations that found he was the victim of shoddy crime scene investigation and outdated theories.
The tragic miscarriage of justice in Willingham's case is not isolated. Many harrowing tales exist: Frank Lee Smith spent 14 years on Florida's death row and was exonerated as a result of DNA testing 10 months after he died awaiting execution.
The number of postconviction DNA exonerations in the US is more than 200. Since 1973, the US has released 135 people from death row due to DNA exonerations. Some were convicted due to mistaken eyewitnesses, others due to police and prosecutorial zeal and misconduct.
People, especially in law enforcement, have a hard time comprehending such stories. Don't we live in a free society where criminals have too many rights and the police's hands are tied up by too many regulations? Every cop knows at least a few criminals who walk around free because we can't charge or convict them.
Yet innocent people are railroaded through our "justice" system, all the way to lethal injections and the electric chair. Why?
The answer lies both in our human and institutional natures. As humans, we tend to believe whatever fits our self-interest, discarding facts that tend to challenge our hypotheses. The errors of deduction can therefore multiply in an investigation when shoddy science is applied or where we rely solely on eyewitnesses. As Willingham's case demonstrates, the combination can be fatal.
Early in my career, my training officer and I responded to an attempted murder investigation. The victim was shot from close range. Thankfully the shooter missed the intended target's vitals and only managed to hit the victim's biceps.