Last week a jury acquitted Roger Clemens on all counts in the perjury prosecution brought against him. So having won this battle, is he a free man? Or can the prosecution attempt to retry the case?

The Fifth Amendment to the United States Constitution provides that “No person shall … be subject for the same offense to be twice put in jeopardy of life or limb.” This so-called Double Jeopardy Clause makes sure that people acquitted of a crime do not face repeated prosecution by zealous government lawyers seeking a conviction. For Clemens, it means he is a free man.

Acquittals differ from hung juries. With an acquittal, the jury has affirmatively determined that the prosecution did not meet its burden of proving guilt beyond a reasonable doubt. If the jury reaches deadlock and cannot agree on its vote — a “hung jury” — the judge will ultimately order a mistrial. In that case, the prosecution has the right to retry the case. Still, the hung jury is usually viewed as a victory for the defendant, and it can cast a shadow over the strength of the government’s case. In fact, it is not uncommon for prosecutors to decide not to retry a defendant in the face of a hung jury.

Neither an acquittal nor a hung jury will prevent a civil lawsuit if the facts support it. Recall the famous O.J. Simpson case. The glove didn’t fit, and the jury did acquit. But O.J. still found himself sued successfully by his late wife’s estate, causing his financial ruin. In Clemens’s case, there’s no obvious “victim” of the alleged crime (lying under oath), and a civil suit seems unlikely.

I didn’t follow the Clemens case closely, so I can’t share a personal opinion on the wisdom of the jury’s verdict or on the relative performance of the prosecution and the defense. I am reminded how important the jury’s power to acquit is in a just legal system. As observed by many and famously recorded by Blackstone: “Better that ten guilty persons escape than that one innocent suffer.”