Last week, a jury of six convicted Guantanamo Bay detainee, Salim Hamdan, of material support to terrorism and acquitted him of conspiracy charges related to September 11, 2001. It sentenced Hamdan to imprisonment for five years and five months.

But, the presiding judge already has indicated that Hamdan will receive five years credit for time served at Gitmo — which means that Hamdan could be released in a few months. The lenient sentence means that the American government will not be able to exchange a light sentence for information, in this case and in future ones.

Hamdan was the bodyguard and driver for Osama bin Laden and according to prosecutors, he was part of Mr. bin Laden’s inner circle, swore allegiance to Mr. bin Laden, attended Al Qaeda training camps, transported weapons for Mr. bin Laden, and helped Mr. bin Laden evade capture by U.S. Special Forces in Afghanistan at a most crucial time — in the weeks after September 11 when American forces were hot on his heels. Hamdan was Mr. bin Laden’s bodyguard and getaway driver. Because of people like Hamdan, Mr. bin Laden has gotten away with murder.

Prosecutors in Guantanamo Bay presented mountains of evidence, lasting nearly two weeks, to six jurors who found Hamdan guilty. America has been criticized for unfair trials that supposedly give prosecutors an edge. But, the facts don’t support that charge. What has been shown over the last few weeks is that the military commissions being held in Gitmo are fair, balanced, and afford detainees fundamental due process.

Many of the early criticisms were like the boy who called wolf. Hamdan wasn’t excluded from his trial, like the defense counsel said he would be. Nor was it a rigged trial conducted in the shadows, like the defense counsel said it would be. Instead, the government went to great lengths to declassify evidence for trial. And Hamdan had an opportunity to present evidence and cross-examine witnesses against him. He had the right to remain silent and had access to thousands of documents and boxes of evidence against him. At times the judge decided issues in favor of Hamdan; other times he decided issues in favor of the government.

Following nearly two weeks of evidence presented by the prosecution team, the defense counsel for Hamdan presented what can only be called a lackluster defense. It steered far away from the facts and presented only one day’s worth of evidence.

The defense relied on a hearsay statement from an alleged September 11 mastermind, Khalid Sheikh Muhammad, who said in writing, because he refused to testify on Hamdan’s behalf, that Hamdan was a low-level participant in the September 11 conspiracy. In Mr. Muhammad’s view, Hamdan was not fit to be a terrorist, just fit to drive them around from place to place.

Even if we believe Mr. Muhammad, who was not subject to cross-examination, under the crime of conspiracy, low level participants are culpable as well. It doesn’t matter that the getaway driver didn’t rob the bank. He is just as culpable as the bank robber, because he made the robbery possible, in the same way that Hamdan made September 11 possible.

What’s more, the defense counsel complained incessantly about the rule allowing hearsay, and then it relied on hearsay from Mr. Muhammad. Ironically, the defense benefited the most by a rule it claimed was unfair.

But, the biggest faux pas made by Hamdan’s lawyers came during their closing arguments. On the heels of its argument that Hamdan was a low level flunky who could only change tires, it simultaneously argued Hamdan offered to help the American government “in a significant way” when the government captured him in November 2001. Hamdan’s lawyer told the jury to “look at the information Mr. Hamdan provided to the United States when it mattered the most,” which has led to speculation that Hamdan may have offered to lead American forces to Al Qaeda.

But, the defense counsel can’t have it both ways. It can’t reasonably argue that Hamdan was privy to the most sensitive information about Al Qaeda in the days after September 11, and simultaneously maintain that he knew nothing. But, the prosecution failed to point out the inconsistency, which saved the defense counsel from its own error. So the jury missed the inconsistency and acquitted Hamdan of conspiracy.

Hamdan’s partial acquittal also can be traced to a legal faux pas from the bench. The judge presiding over Hamdan’s trial gave incorrect instructions to the jury. He told them that Hamdan could only be found guilty of a war crime if the surface-to-air missiles, which were found in the trunk of his car when U.S. forces arrested him, were intended to be used on innocent civilians.

Under this instruction, if Hamdan intended these weapons to be used against American forces, he can’t be found guilty of a war crime. This instruction is contrary to International Law and the Geneva Convention. Because the prosecution team did not object until after the jury began deliberating, the judge did not revise his instruction. Not surprisingly, the jury followed the erroneous instruction and acquitted Hamdan of charges related to the missiles found in his car when he was arrested.

Trials are always easier in hindsight. Despite the various errors and inconsistencies in the defense theory and the jury instruction, which favored the defense, one fact is clear: Hamdan’s trial was transparent, and fair. Fair trials result in some acquittals and some convictions. After all, the scales of justice tip both ways.

Ms. Rotunda, a law professor at Chapman School of Law and a former Gitmo prosecutor, is the author of “Honor Bound: Inside the Guantanamo Trials.”