Dateline: June, 2007, Issue 5
Juries are sometimes provided a lesser charge on which to convict a criminal defendant in addition to a primary charge sought by prosecutors.
Koch and Devine (1999) examined how a lesser included charge affects convictions by criminal juries. Jurors (individually) and juries (after deliberations) with the option to convict on a lesser charge (manslaughter) produced more overall convictions than juries receiving only a primary charge (murder), but only when reasonable doubt was undefined (i.e., all that was said was that the prosecution needed to convince "beyond a reasonable doubt"). When reasonable doubt was defined as "proof that leaves you firmly convinced of the defendant's guilt," a lesser included charge did not produce more overall convictions.
The researchers concluded that jurors with a choice of charges were more likely to feel the defendant was guilty of some crime than jurors who received only the murder charge, and this effect was particularly noticeable when reasonable doubt was not well defined.
Source Koch, C. M. & Devine, D. J. (1999). Effects of reasonable doubt definition and inclusion of a lesser charge on jury verdicts. Law and Human Behavior, 6, pp. 653-674.