Wednesday, January 30, 2008

The Unreliability of Confessions

From BPS comes this summary of a study that was just published:
Not surprisingly, confessions are extremely persuasive in court, but according to Jessica Klaver and colleagues, all too often these confessions are false, leading to the wrong person being found guilty.

Now Klaver's team have used an elegant laboratory task to compare two types of interrogation technique and found that it is so-called 'minimising' questions and remarks - those that downplay the seriousness of the offence, and which blame other people or circumstances - that are the most likely to lead to a false confession.

Over two hundred Asian and Caucasian students were invited to take part in what they were told was a test of their personality and typing skills. During the typing part of the task, they were warned in advance that pressing the 'Alt' key would cause the computer to crash and a loss of all data. Subsequently, when the participants were required by the task to type 'Z' (near the 'Alt' key), the researchers contrived it so that the computer duly crashed, and the participants were accused of pressing the 'Alt' key.

Next the students were subjected to either 'minimising' remarks (e.g. "Don't worry. It was just an accident" and "This programme seems not to be working lately") or 'maximising' remarks that played up both the evidence for the student being guilty and the seriousness of the alleged error (e.g. "You must have pressed it" and "We have run over 50 people on this test in the past three weeks and the computer hasn't crashed once").

Overall, 43 per cent of the students subsequently signed a confession statement, stating falsely that they had indeed pressed the 'Alt' key. Crucially, the confession rate was four times higher among the students subjected to minimising remarks as opposed to maximising remarks.
* * *
Add to that the fact that psychologists have long known that eyewitness testimony is extremely unreliable and manipulable, as is human memory more generally. One fairly recent study:
Victims who get a good long look at violent criminals are unlikely to identify them accurately later, Yale and U.S. Navy researchers have found.

This caveat follows from a unique study of 509 Navy and Marine officers undergoing elite survival training at Fort Bragg, N.C.

Results suggest that police and juries may give eyewitness testimony too much credibility, said Dr. Charles A. Morgan III, a Yale psychiatrist and lead author of the study.

"Memory in healthy people is not inherently terribly accurate. There's a substantial amount of error," Morgan said. "Maybe we should demand more evidence."

* * *

Officers who were absolutely positive that they had selected the right person were no more likely to be correct than officers who expressed some doubt.

"Unfortunately, that's what people on juries listen to," Morgan said.
These sorts of studies are reason to be cynical not just about the death penalty, but about the entire criminal justice system. What does it say that the evidence deemed most reliable by juries -- confessions and eyewitness accounts -- might often be false? At the same time, lots of crimes are indeed committed each year, and it seems implausible that the criminal justice system would manage to catch only the innocent people. It's a quandary. Maybe people who are actually tried and convicted by a jury are more likely to be innocent (because of the possibility of faulty testimony or confessions) than are people who plea bargain knowing that they're guilty.


Blogger Stephen said...

The problem is that at some point you throw out every type of evidence and end up with none at all.

1:02 PM  
Blogger Big Yellow Forehead said...

I have to agree to a degree. Relying solely on evidence could become extremely difficult, especially if the crime were to occur outdoors in a big city, or in a densely populated area. Nonetheless, the blog doesn't state that ALL witnesses are incorrect, so there is still some hope in witness testimonies...

12:21 PM  

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