How Many Jurors Does a Good Verdict Require?

I watch trial coverage on TV and like shows and movies that include legal drama, so I well know that an American criminal case is decided by twelve jurors.  Well, that's what I thought, but an article on "The Mathematics of Jury Size," by Chris Gorski of Inside Science News Service points out why this Blind Bambi isn't always as smart as he thinks he is.

He explains that the customary juror count of twelve dates back to the decision of an 8th century Welsh king, who established jury trials and based their size on the fact that Jesus had twelve Apostles.  The U.S. Constitution does not specify 12-person juries nor does it require unanimous decisions, and some states do, in fact, employ some variants of the traditions.  For example, states like Florida, Connecticut, and others have either considered or actually used smaller juries of six or nine people instead.  In Louisiana, verdicts may only require agreement of nine out of twelve jurors.  In 1978, however, when Georgia tried to pare down to a five person jury for certain criminal trials, the Supreme Court stepped in and disallowed it.

Anyway, Jeff Suzuki, a mathematician at Brooklyn College in New York, recently presented research into the likelihood of conviction given variances in jury conditions such as its size.  Not surprisingly, his model suggests that smaller juries are more likely than larger juries to convict when the defendant appears less certain to be guilty.  As he points out that the accuracy of jury decisions is much more complicated than the number of people entrusted with the decision, it appears that the answer for optimum jury size is (again not surprisingly) not clear.