Bob Self / The Florida Times / REUTERS Marissa Alexander in a Duval County courtroom in Jacksonville, Fla., on May 3, 2012

Critics of the George Zimmerman verdict argue that the Florida criminal-justice system is discriminatory — and that a black defendant would not have been acquitted for doing what Zimmerman did. Now they are rallying on behalf of a case that they say proves their point. Marissa Alexander fired a single shot at her abusive husband and missed. She later invoked the “stand your ground” doctrine. Verdict: guilty, with a 20-year prison sentence.

Alexander’s supporters have been protesting across Florida in recent days, demanding that she be pardoned. Alexander’s self-defense claim, like Zimmerman’s — and most others — is messy, with facts that can be interpreted in a variety of ways. What is clear, however, is that the 20-year sentence and the Florida law that mandated it are a travesty of justice.

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Alexander, a mother of three, was convicted in March 2012 of three counts of aggravated assault with a deadly weapon. In August 2010, she got into a dispute with her husband Rico Gray in their Jacksonville kitchen. Alexander ended up getting a handgun out of the garage and firing one shot in the direction of Gray and his two sons, missing everyone.

Alexander’s supporters emphasize that Gray had a long history of spousal abuse and that she had recently obtained an order of protection against him. And they point to a particularly appalling sound bite from Gray: “I got five baby mamas, and I put my hand on every last one of them except one.” They say she was in reasonable fear that she would be killed or injured and fired a warning shot to protect herself — well within what the “stand your ground” law allows.

Prosecutors see it differently. They insist that Alexander did not stand her ground: rather, she left the scene, got a handgun and then returned. They say Gray made a call to 911 that indicated that he thought his life was in danger and had been trying to flee. (There have been reports that Alexander was physically abusive toward Gray.) Alexander’s prosecutors had an advantage over Zimmerman’s. Trayvon Martin was not alive to contradict Zimmerman’s self-defense claim. But the three people Alexander shot at were around to testify against her.

(MORE: Where Was ‘Stand Your Ground’ for Marissa Alexander?)

It is frustrating to admit, but Alexander’s self-defense claim is a close call, and ultimately a very fact-specific one. If she really was trapped and reasonably feared that she was in danger of death or serious injury, she had the right to shoot in self-defense. But if Alexander had a clear path of escape, she should have fled before putting not just Gray but two innocent children at risk of being shot. The jury clearly did not see the facts her way. (It casts some doubt on their verdict, however, that they reached it after just 12 minutes of deliberation.)

There is something undeniably galling about seeing Alexander sent away for 20 years, while Zimmerman, who shot a 17-year-old to death, walks free. But it is not clear that the answer is to broadly protect people who shoot guns in domestic situations and then claim self-defense. The more expansively courts interpret “stand your ground” in circumstances like Alexander’s, the more bullets are likely to be ricocheting through family homes, and the more deaths there are likely to be.

What is clear is that Alexander’s 20-year prison sentence is horrific. There is a different Florida law that is responsible for the length of the sentence: the so-called 10-20-Life statute, which says that if someone is convicted of an aggravated assault in which they discharge a firearm, they must be sentenced to 20 years in prison, regardless of mitigating circumstances. When Circuit Judge James Daniel sentenced Alexander, he declared that once the state proved its case, “the decision on an appropriate sentence” was “entirely taken out of my hands.”

Alexander’s case is less about “stand your ground” than about the horrors of excessive, inflexible sentencing laws. Whatever crimes legislators were thinking of when they decided to establish the mandatory 20-year prison sentence in 10-20-Life, there is no way they included a battered woman feeling threatened and firing a single shot that missed her abusive spouse. Given the facts of her case, prosecutors were being overzealous in charging Alexander with a crime that is punishable by a 20-year sentence.

There have been growing calls for Florida to repeal its “stand your ground” law. But people who care about making Florida’s criminal-justice system fairer should work just as hard to repeal the cruelly inflexible 10-20-Life statute. More immediately, Alexander’s sentence should be commuted, because it fails the most basic test of just punishment: it does not fit the crime.