Recently I was asked about the issue of whether you are better off with a six or twelve person jury. Even though it is probably moot for most of our cases because we don’t have a choice, it is an issue worth considering. In Washington state, where I practice, the rule provides that a party can request a six or twelve person jury, but the other side can demand a twelve person jury if six is initially requested. The insurance companies in tort cases don’t allow six person juries in my experience so that even though I request the smaller jury, they demand the full jury. Here is the situation regarding the issue as I know it.
Since the 1970’s there has been considerable research including empirical studies on jury size and even the U.S. Supreme court has considered the issue of six vs twelve person juries. Numerous books exist about research done on the function of juries by social scientists. No scientifically accurate conclusions can be drawn but we have some information that is probably reliable. One study is particularly worth reviewing was published by The National Center for State Courts in 2004 published a very comprehensive study entitled "Does Jury Size Matter?" but there are a lot of books on research about jury size and jury deliberation.
Here are some observations that appear to be reliable based upon the research:
In a study involving some 15,000 jurors it appeared that larger juries (more then six) are more likely to be representative of the community with minority groups, they deliberate longer, they end in a hung jury more often and they probably recall testimony more accurately then six person juries. (A Meta-Analysis of the Effects of Jury Size by Saks and Marti) Hans Zeisel’s famous research in 1977 confirmed these conclusions as well.
To some extent the issue depends upon the objective:
Economic considerations? Six person juries cost less, takes less time on voir dire, reach verdict quicker etc. The judiciary favors smaller verdicts when it comes to enconomic considerations.
Peer representation considerations? Smaller juries have less mix of gender, religion, race etc. hence we have a number of cases considering size and constitutional isues. Most hold that in criminal cases less then 12 person juries are "inferior" as not representative of the community. Juries are supposed to be a cross section of the community and 6th Amendment rights require a fair jury. There are constitutional implications in the use of preemptive strikes in jury selection in both civil and criminal cases.
It also depends upon the type of case:
Criminal- If you are the defendant you want more jurors for better chance of controversy, hung jury etc. The ABA position is that a jury of less then twelve is not representative of the community. The U.S. Supreme court has considered constitutional issues in that regard.
Civil cases: if you are a defendant you want more jurors for same reason as the defendant in a criminal case, but If you are the plaintiff you want a jury that is less likely to argue among themselves, less likely to compromise in order to reach a verdict and more likely to render a unanimous verdict without a lot of controversy. Since our problem is the conservative on the jury, small group dynamics dictate it is better for the plaintiff to have less chance of controversy. Obviously, that also means if you have a lousy case you are more likely to get a quicker defense verdict with a smaller group, but even if you have twelve jurors with a lousy case your outcome is probably the same. It will just take longer.