According to a pair of recent studies, how one answers that question goes a long way in determining how you act. Kathleen Vohs and Jonathan Schooler had participants read a passage in Francis Crick's book The Astonishing Hypothesis that espoused a very deterministic view of our brains. Others read another passage from the book that discussed consciousness but never mentioned free will.
Afterward participants were asked to take a math quiz on a computer. During the quiz they were told there was a software malfunction and that they needed to hit the space bar after the question was presented so that the answer did not appear on screen. It turned out that the people who had read the first passage were far more likely not to hit the space bar - in other words, cheat - than the people who read the second passage.
Roy Baumeister conducted a study in which the participants were split into three groups. The first group was told to read statements that were deterministic in nature. The second group read statements that spoke of free will. The third group, or control group, was given neutral statements to read.
In the first experiment, participants were given scenarios and asked what they would do to help the person in trouble. The people who read the deterministic statements were found to be less likely to help out. In the second experiment, participants were told that a classmate's parents had been killed in a car accident and that the classmate would have to drop out of school without some kind of financial help. Again, the people who read the deterministic statements were less likely to help out. Finally, participants were given the opportunity to add hot sauce to a dish being served to someone who was averse to spicy foods. You guessed it, the people who read the deterministic statements were more likely to pour it on.
Knowing a potential juror's attitude toward the debate between determinism and free will could be vital to trying your case. Those who tend toward the determinism, or nature, side of the argument may very well believe that your client is somehow genetically disposed to a life of crime which wouldn't bode well back in the jury deliberation room.
"Free Will and Ethics" The Frontal Cortex, 12/17/09