6 Common Causes

As of April, 2016, The National Registry of Exonerations lists 1,740 innocent people since 1989 who were wrongly convicted of serious crimes and have since been exonerated. That’s more than 60 every year; a rate that continues to grow with the improvement of DNA testing methods and databases.

How can such grievous mistakes be so common?


Eyewitness misidentification is the single biggest problem, contributing to more than 75% of the wrongful convictions that have later been overturned because of DNA testing. Literally hundreds of studies have demonstrated that eyewitness identification is often inaccurate.

Why is this so prevalent? Partly because of simple human error (our eyes are not camcorders, and our memories are not predictable storage devices like computer hard drives), and this is exacerbated in many cases by poor procedures of law enforcement in dealing with witnesses.


It seems incredible, but another fact is that, of those wrongful convictions overturned on the basis of DNA evidence, a full 25% had made a false confession or self-incriminating statement.

Why would an innocent person confess to a crime they did not commit? There are a number of factors, and mostly they fall under 3 categories: duress, diminished capacity, or ignorance. Duress can be either through the stress of the situation, or because of police or prosecutorial misconduct. Diminished capacity may be due to their mental state (temporary or chronic), or because of intoxication. And some accused persons are simply ignorant of the law or of their rights, or may misunderstand their situation.


In 15% of wrongful convictions, the case presented against the innocent at trial included statements by incentivized witnesses (often referred to as “snitch” testimony). As many as 45% of capital cases later overturned included one or more such witnesses. Jailhouse “snitches” will often give false statements in the hope of gaining either favors in prison or reduced sentences.


Television shows like “C.S.I.” can give the public the impression that forensics are an exact science that can always be relied upon to produce incontrovertible “smoking gun” evidence. While forensics are a vitally important part of criminal investigation, however, there continue to be instances of errors that result in wrongful convictions. These errors can be because (1) the methods employed are unproven or not consistently reliable, (2) the findings are expressed with exaggerated and misleading confidence, or in some cases (3) the forensic evidence is fraudulent.


When law enforcement conclude that a suspect is guilty, there can be a tendency to focus on that person, selecting the evidence that helps to build the case against them to the exclusion of other evidence that points away from their guilt.

This “tunnel vision” can continue beyond the police investigation to the prosecution phase. Prosecutors, feeling that the preponderance of evidence points to the guilt of the accused, may suppress evidence to the contrary. The Supreme Court ruled on this in Brady V Maryland (1963) as a violation of the due process required under the Fourteenth Amendment, but cases are regularly reported where it still occurs.


When an arrested person is read their Miranda Rights they are told: “You have the right to an attorney. If you cannot afford an attorney, one will be provided for you.” This is required by the Sixth Amendment which guarantees criminal defendants the right to counsel. But what of the “quality” of that counsel?

In 1984, the Supreme Court established standards for determining when a defendant’s right to counsel has been violated because of said counsel’s inadequate performance (Strickland V Washington). Such ineffectiveness, however, is usually difficult to prove. From instances of gross negligence and malpractice through to honest mistakes due to inexperience or workload, poor lawyering continues to result in wrongful convictions.