Prof. Brandon Garrett (with the help of a team of research assistants) found out all he could about the first 250 DNA exonerations, gathering trial transcripts (when available), news coverage, appellate records, and the records from state post-conviction proceedings and federal habeas cases. Then he mined the data: How many of the exonerated people had confessed falsely? How many had been mistakenly identified by one or more eyewitnesses? How many were prosecuted with questionable forensic evidence (hair analysis, for instance, does not prove much of anything)? How many years did it take from initial conviction to eventual exoneration?
He presents the results in Convicting the Innocent: Where Criminal Prosecutions Go Wrong (KF9756 .G37 2011 at Classified Stacks). The results are disturbing—but can also be instructive.
I think it's worth noting that the wave of DNA convictions from the 1990s to now will taper off. The wrongly convicted people had been tried when sophisticated DNA tests were not available. It was only possible to seek post-conviction DNA tests if there had been enough DNA left at the crime scene and if the police had preserved the evidence. Now if the crime is one where DNA evidence is available, it's very likely that it will be tested before trial—avoiding trials of people like the exonerees and keeping law enforcement on the investigation until the actual rapists and murderers are caught.
But cases with DNA evidence are just a minority of crimes. The exonerations were typically in rape or rape-murder cases, because those are cases where the criminal most often leaves semen or blood. But think of other, equally serious crimes: Drive-by shooting? No DNA at the scene. Murder when the body is not found for many years? Probably not enough uncorrupted DNA. Murder for hire? No DNA from the person who hired the killer and probably no DNA from the killer, assuming he or she is careful. Arson? No DNA. Robbery? Probably no DNA. Murder of a family member? If there's DNA at the scene or on the body, there's an innocent explanation.
The DNA exonerations can teach us lessons to be used in all cases. First, innocent people sometimes do confess. Garrett gives many examples. The defendants who confess falsely are often young, developmentally disabled, mentally ill, or a combination, and they have often been interrogated very intensely for a long time. Recording all interrogations would benefit everyone. Obviously, it would help suspects who are coerced or manipulated. It would also protect police and prosecutors from false claims by defendants that their interrogations had been coercive. Second, the exonerations make clear that eyewitnesses can be mistaken when they identify suspects. There are ways to improve identifications—the say line-ups and photo arrays are conducted—and, again, improving the process would help everyone. The books suggests many other facets of prosecution and review that could be improved.
If you want answers to the questions I opened with—how many false confessions, how many mistaken identifications, and so on—you can read the book. You can also browse the appendix, in which Garrett summarizing his findings in a series of graphics and tables.
Prof. Garrett has collaborated with the Innocence Project to create a multimedia website, Getting It Right, that includes videos, illustrative cases, suggested reforms, and links to research in six areas:
- Eyewitness Identification
- Law Enforcement