On Tuesday, 25-year-old Casey Anthony was acquitted of killing her two-year-old daughter in a capital murder case that captivated national audiences for some three years. We asked Northeastern University law school professor Daniel Givelber, whose scholarship focuses on criminal law, criminal procedure and capital punishment, to assess the controversial verdict.

Why did jurors find Casey Anthony not guilty of murdering her daughter? What must prosecutors prove in cases in which the defendant faces the death penalty?

A prosecutor needs to persuade the jury of a defendant’s guilt beyond a reasonable doubt. There is no way to know why a jury acts as it does, since jurors are not required to explain their verdicts. News reports indicate that the case against Casey Anthony was entirely circumstantial — there were no witnesses who testified that they observed her commit or cover up the crime — and the prosecution may not have had enough evidence to persuade the jury that it was Casey and not someone else who committed the crime.

The prosecutor’s burden to prove the defendant’s guilt is no greater in a death penalty case than in any other homicide prosecution; there is a separate proceeding following a guilty verdict to determine if a defendant should die. Since Casey Anthony was not convicted of a capital crime, such a proceeding will never be held.

In high-profile cases, how do defendants who are charged, and then acquitted of capital murder, go about living so-called “normal” lives?

With great difficulty. In our system, an acquittal is not an exoneration — it simply means that the state has failed to persuade jurors of guilt beyond a reasonable doubt. Jurors may believe that a defendant is probably guilty and still acquit because they have been instructed to convict only if they are convinced beyond a reasonable doubt. This means someone who has been acquitted may still be treated by our legal system and society at large as though she most likely committed the crime.

The Casey Anthony verdict received more Tweets than last season’s Super Bowl. Why did this case generate so much national attention?

To state the obvious, the crime was horrible, the defendant was photogenic, and the evidence was equivocal. The case attracted so much attention for many of the same reasons that detective fiction continues to be so popular; many of us find mysteries interesting, and the death of Casey Anthony’s child has been and still remains very much a mystery.