A federal appeals court came down hard Tuesday on use of evidence of prior bad acts in a context that implies a defendant acted consistently with a predisposition toward crime.

The U.S. Court of Appeals for the Third Circuit, in State v. Smith, 12-1516, ordered a new trial for a man convicted of threatening an FBI agent and other charges, finding the judge should not have admitted evidence of his involvement in a prior drug deal.

In 2010, Durrell Smith, carrying a handgun, had walked toward an unmarked vehicle in Newark where the agent and other officers were conducting surveillance. He later claimed he did not know who was in the car but feared for his life because of a recent shooting in the area involving a similar car.

Before trial, the government moved to admit testimony from another agent that, two years earlier, he saw Smith conduct a drug deal on the same corner.

Federal Rule of Evidence 404(b) bars prior-crime evidence "to prove a person's character in order to show that on a particular occasion the person acted in accordance with the character" but allows it for other purposes, such as to show motive.

Over Smith's objection, U.S. District Judge Mary Little Cooper in Trenton admitted agent Michael Brooks' testimony, instructing the jury it was for the limited purpose of deciding whether Smith's motive was "offensive, rather than merely defensive." She told the jury not to consider it as proof Smith had a bad character or a propensity to commit crimes.

The jury convicted Smith on all charges. He was sentenced to 30 years.

On appeal, Judges Dolores Sloviter, Julio Fuentes and Jane Roth said motive was relevant, but besides establishing a proper purpose, the proponent of the evidence must establish "a chain of inferences, no link of which is based on a propensity inference."

Fuentes, writing for the panel, said that for the prior sale to speak to Smith's motives in 2010, one must assume something about his character based on that evidence — that he was then a drug dealer — and infer that he acted in keeping with that character in 2010 and had a motive to defend his turf.

Fuentes also said the lack of similarity between the two events, and their temporal separation, weaken "the force of the evidence standing on its own, to the point where the jury has to make inferences about Smith's character from his 2008 conduct in order to learn something about Smith's 2010 motivations from that conduct."

Cooper failed to balance the prejudicial nature and probative value of the testimony, as required under R. 403, and failed to consider the diminished probative value of the 2008 drug deal in light of the fact that it did not involve firearms, and that the 2010 incident did not involve drugs, the panel said.

Smith's lawyer, Kevin Carlucci of the Office of the Federal Public Defender, did not return a call.

The government was represented by Assistant U.S. Attorney Steven Sanders.

Spokeswoman Rebekah Carmichael said the office is considering its options.