Yes, a jury is drawn from a pool of randomly selected individuals, yes. But the pool is first filtered, by striking (1) people who appear to the judge to have too much potential for bias; (2) people who convince the judge they have a good excuse for not serving on the jury; and (3) up to X people peremptorily struck by the lawyers, where X typically equals 3 per side.

(In technology-related cases, item 3 often results in the exclusion from the jury of anyone who knows anything about the technology---one or another team of lawyers will want the jurors to know only that which was presented to them for the first time at the trial.)