Prosecutorial Misconduct

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"Tunnel vision" is a common tendency we are all susceptible to -- the shaping of information to support an already-decided conclusion, rather than a determination formed solely by the facts at hand. In the criminal justice system, this allure of confirmation bias exacerbates the other various flawed legal procedures, leading police and prosecutors to ignore other leads to pursue the person they had determined to be the perpetrator.  This "tunnel vision" within the prosecutorial branch of the criminal justice system can lead to investigative and trial misconduct in order to secure to secure the conviction of a predetermined, concealing  evidence or resisting comprehensive investigations to secure a conviction.

Prosecutors committed misconduct in 30% of known exonerations -- primarily concealing exculpatory evidence, trial misconduct, and witness tampering. In state cases, prosecutors and police committed misconduct at around the same rate, but in federal exonerations, prosecutors committed misconduct more than double the amount as police. And when this was extended to federal exonerations for white-collar crimes, prosecutors committed misconduct seven times as often as police. 

The most common type of official misconduct was found to be concealing evidence that would be helpful to the defendant's case, done by prosecutors and police officers alike. The National Registry of Exonerations specifies two basic categories of exculpatory evidence that were concealed into two categories:

Substantive evidence of innocence. In 30% of exonerations, law enforcement officials concealed substantive evidence that would have supported the defendants’ innocence claims: alibi evidence, evidence about alternative suspects, and biological evidence that excluded the defendant from the scene.

Impeachment evidence. In an overlapping third of all the cases -- 805/2,400 -- police and prosecutors concealed evidence that would undermine witness testimony that testified against the defendants. This included previous statements in which witnesses had said the opposite of their court testimony, attempts to retract their accusations, or deals made with witnesses to cut their prison time in return for a testimony. It was notably prevalent in murder exonerations -- occuring around 3x the amount in comparison to those of non-homicidal crimes.