Readers interested in the history and development of jury nullification in Indiana should read "The Right to Ignore the Law: Constitutional Entitlement Versus Judicial Interpretation" by Indiana Supreme Court Justice Robert D. Rucker (33 Val. U. L. Rev. 449, 470 (1999)) (then a State appellate court judge). I'm not expert enough to judge law reviews, but as a layman, I found it to be quite good.

The case law in Indiana revolves exclusively around the instructions of the judge to the jury -- and what about Art I, Sec 19 those instructions may not contain. The Indiana Supreme Court had until recently come to view this provision as an historical artifact: Indiana has never had such despotic governments as have plagued Great Britain; judges are professionally trained in the modern era, and juror are not likely to be as (un)qualified as the presiding judge, as was often the case in the 19th-Century; and the Hoosier constituency is not currently overwhelmingly composed of Jacksonian Democrats, who framed our constitution. As such, the words "to determine the law" become meaningless, and jury instructions amount to tautology. Rucker provides a typical wording:

Since this is a criminal case the Constitution of the State of Indiana makes you the judges of both the law and the facts. Though this means that you are to determine the law for yourself, it does not mean that you have the right to make, repeal, disregard, or ignore the law as it exists. The instructions of the court are the best source as to the law applicable to this case. (emphasis added)

Using an originalist (?) line of examination, then-Judge Rucker attempts to breathe new life into Art I, Sec 19:

In a criminal prosecution, the power of government is in full force. Even the caption of the charging instrument is imposing: "The State of Indiana v. ." The core value of checking and controlling that power through the voice of ordinary citizens is consistent with the spirit of Jacksonian democracy. Certainly the jury's right to determine the law meant something to the framers. If it did not mean that the jury could alter, abolish, or amend the law, and if it did not mean that the jury could set aside the law on the basis of having a differing opinion of what the law was, then what did it mean? Considering the apparent purpose for which the provision was adopted, as informed by the history of Indiana's constitutional scheme, one may reasonably conclude that it means the jury has a right not to apply the law when their conscience so dictates.

. . . [A]n instruction telling the jury that the constitution intentionally allows them latitude to "refuse to enforce the law's harshness when justice so requires" would be consistent with the intent of the framers and give life to what is now a dead letter provision.

It is clear that the jury already has the unreviewable power to acquit in the face of evidence, and a trial judge cannot direct a verdict of guilty "no matter how overwhelming the evidence." Informing the jury that they have the right under the Indiana Constitution would do little more than to underscore that power. (notes omitted, second emphasis added)

In my mind, this is a powerful and convincing argument, and libertarians may have been pleased to see Rucker elevated to the Supreme Court in the same year that he wrote this law review. Oddly, and unfortunately, his writings have not been bourn out in practice. In 2003, the Indiana Supreme Court went out of its way to address the issue of jury nullification in trial court instructions in Holden v. State (788 N.E.2d 1253 (Ind. 2003)). As summarized by John Laramore in his survey, "Constitutional Law: Indiana Constitutional Developments" (37 Ind. L. Rev. 929 (2004)):

In Holden, however, the court rejected just the kind of instruction suggested by Justice Rucker's article, and it did so in a unanimous opinion written by Justice Rucker. The opinion briefly reviewed the history of jury nullification, defined as the jury's "right to return a verdict of not guilty despite the law and the evidence where a strict application of the law would result in injustice and violate the moral conscience of the community." The court stated that

early case authority in this state stood for the proposition that the jury's law determining function meant that the jury could "disregard" the instructions of the trial court. However, on closer examination it appears that the right to disregard the trial court's instructions has never been equated as a right to disregard "the law."

That is, the jury is permitted to construe the law in a manner different than the judge, but not to ignore it altogether. The court concluded:

Although there may be some value in instructing Indiana jurors that they have a right to "refuse to enforce the law's harshness when justice so requires," the source of that right cannot be found in Article I, Section 19 of the Indiana Constitution. This Court's latest pronouncement on the subject is correct: "It is improper for a court to instruct a jury that they have a right to disregard the law. Notwithstanding Article I, Section 19 of the Indiana Constitution, a jury has no more right to ignore the law than it has to ignore the facts of a case."

The court affirmed the trial court's decision not to permit the instruction suggested by Justice Rucker's article. (notes omitted)

Basically, the Court merely re-affirmed the jurors' right to nullify (how nice of them) while precluding judges (and by extension defense counsel) from informing juries of this right.