WASHINGTON — After a jury found a man guilty of several gun and drug offenses, he took his case to the Court of Appeals for the District of Columbia Circuit. In the spring of 1998, two of the judges on a panel that heard his case agreed to vacate two of his convictions, saying that the evidence was too thin to support one, and the trial judge had made a mistake that tainted the other.

But the third judge on that panel, Merrick B. Garland, a former federal prosecutor whom President Bill Clinton appointed to the court a year earlier, sharply disagreed. In a dissenting opinion, Judge Garland — who is now President Obama’s nominee for the Supreme Court — insisted that the evidence was good enough, and that the trial judge’s supposed mistake did not matter.

Four months later, Judge Garland was assigned to a different panel hearing an appeal in another drug-related case. The two other judges threw out a conviction, saying that a prosecutor had violated the defendant’s right to a fair trial by misquoting a witness’s testimony during closing arguments in a way that suggested the evidence was stronger than it was.

Once again, Judge Garland dissented. The prosecutor, he wrote, had made an “innocent” mistake, and the appeals court should overturn the results of a trial only for “the most egregious of these kinds of errors.”