It hard to tell when a juror is taking the law into his own hands. The only people in the room deliberating are the 12 who have been picked to serve, so unless one of them speaks up, no one knows why a jury reaches the conclusion it does. Nor can anyone know what motivates a particular juror. If jurors vote not to convict because they don't believe the nation's drug laws are fair, they may disguise their true feelings by simply saying the evidence wasn't there or the prosecution didn't make its case. Otherwise, they risk being ejected from the jury box.
Prosecutors see it as vigilante justice, but defense lawyers have a complicated response.
Few endorse nullification as a payback for race discrimination or other social grievances, but they also recognize that, if a juror does hold out on conviction, that's good for their client. Some of the most sensational cases, or at least most publicized, arise when the subject of race does. In the recent case against former agriculture secretary Mike Espy, accused of accepting illegal gratuities, independent counsel Donald C. Smaltz asked the judge to specifically instruct jurors not to consider the fact that Espy is African American. Smaltz said he was making the request because Espy's lawyer suggested to jurors that Espy was prosecuted because he is black. Smaltz was turned down, but the daring strategy comes as fresh evidence that prosecutors increasingly believe they need to head off social vindication in the jury box.