Wednesday, May 20, 2009

The DNA effect

Fearful that a jury will accept DNA evidence as definitive as a result of the so-called "CSI Effect?" 

New research indicates that your fears may be somewhat overblown. Jurors tend to be somewhat skeptical about the reliability of DNA evidence, but, when that evidence matches the defendant, guilty verdicts tend to follow.

Juror research demonstrates that the presence of DNA evidence tends to enhance the credibility of other evidence introduced during the trial. Thus we have the dreaded "feedback loop." We are then left with the question of which came first: jurors' reliance on DNA evidence to support a conviction or juror's reliance on the other evidence?

The studies also indicate that jurors give more weight to DNA evidence when it's couched in terms of percentages rather than ranges. In other words, a juror is more likely to accept the DNA evidence when the state's expert says there is a --% chance that the defendant committed the crime rather than there is a one in a -- chance that a person selected from the general population at random was present at the scene.

Given this, the way in which DNA evidence is presented at trial can affect the way in which a juror looks at the rest of the evidence presented.

Statistician anyone?

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