Causes of Wrongful Convictions

Note: Nearly half of the cases included more than one reason for a wrongful conviction. Therefore the total of the cases in the chart equals more than 86.
In 2001, the Center on Wrongful Convictions at Northwestern Law School analyzed the cases of 86 death row exonerees. They found a number of reasons why innocent people are wrongly convicted in capital cases. The reasons included:

eyewitness error - from confusion or faulty memory.
government misconduct - by both the police and the prosecution
junk science - mishandled evidence or use of unqualified "experts"
snitch testimony - often given in exchange for a reduction in sentence
false confessions - resulting from mental illness or retardation, as well as from police torture
other - hearsay, questionable circumstantial evidence, etc.

Read the Full Report
Attachment A
Attachment B
Attachment C

For more information about the reasons for wrongful convictions, see:

General:

Convicting the Innocent: Aberration or Systemic Problem? by Rodney Uphoff, University of Missouri School of Law

Government Misconduct:

Government Misconduct by the Innocence Project
Police Misconduct by the Center on Wrongful Convictions
Electronic Recording of Custodial Interrogations by the Justice Project

Snitch Testimony:

The Snitch System by the Center on Wrongful Convictions
Jailhouse Snitch Testimony: A Policy Review by the Justice Project

Other:

Bad Lawyering by the Innocence Project

Eyewitness Error:

Eyewitness Misidentification by the Innocence Project
Erroneous Eyewitness I.D. by the Center on Wrongful Convictions
Eyewitness Identification: A Policy Review by the Justice Project

Junk Science:

Forensic Science Misconduct by the Innocence Project
Unreliable and Limited Science by the Innocence Project
Junk Science by the Center on Wrongful Convictions
Informants/Snitches by the Innocence Project

False Confessions:

False Confessions by the Innocence Project
False Confessions by the Center on Wrongful Convictions