Voir dire can be used to strategically put a leader on a jury that will have great influence over others who may be led like sheep. Hiring a firm to scour the history of people in a jury pool is not illegal. Jus saying that it may look like the lawyers are doing the deciding but probably not.

The mob would simply threaten a jury member or two. Now there is practically a spooky neuroscience devoted to jury selection in big cases.