What does Odell Hallmon's reversal mean for the Curtis Flowers case?

There are two reasons why Odell Hallmon's testimony was so essential to the state's case against Curtis Flowers.

The first is that Hallmon's statement — that Curtis Flowers confessed to him in prison — was the singular piece of direct evidence the prosecution had. Everything else was circumstantial, from the people who said they saw Flowers walking through Winona on the morning of the Tardy Furniture murders to the bullets investigators pried out of a stump at Doyle Simpson's mother's house and matched to bullets found at the scene.

The difference between direct and circumstantial evidence is a formal one. Direct evidence can prove a fact on its own. Circumstantial evidence is one step removed. If you see drops of water falling from the sky, you know that it's raining. If you see a person come inside dripping wet, you can deduce that it's raining. But there are also other possibilities: Maybe the person is drenched in sweat or just fell in a swimming pool.

Put another way, in a purely circumstantial case, all the evidence could be true and still might not point to the defendant's guilt to the exclusion of all other possible explanations. Maybe you believe all the witnesses Doug Evans put on the stand who said they saw Flowers walking. But that only proves that Flowers took a long stroll around town on the morning of July 16, 1996. Maybe you believe that Simpson's gun was the murder weapon, but that doesn't prove that Flowers ever stole it or used it himself.

A circumstantial case isn't always weaker than one with direct evidence. "There's the quality of the evidence and there's the quantity of the evidence," said Eve Primus, professor of evidence and criminal procedure at the University of Michigan Law School. "The direct versus circumstantial speaks only to the quality, it doesn't speak to the quantity." An abundance of circumstantial evidence can strongly indicate guilt if it's impossible to explain in any other way.

If forty people walk into your office, and they're all wearing galoshes and carrying umbrellas and are soaking wet, it's almost certainly raining outside, for instance. Still, the state would almost always prefer to be armed with a piece of direct evidence.

Cases based on circumstantial evidence come with certain legal safeguards. Appeals courts consider trial errors more harmful in a circumstantial context. And during trial, if the state's case is wholly circumstantial, the jury can be given special instructions about its potential shortcomings. In Mississippi, a judge will say, "If you can draw two or more reasonable conclusions from the circumstantial evidence, and one of those reasonable conclusions points to innocence and another one to guilt, then you must accept the one that points to innocence."

"Part of why the defense wants [this instruction] is because it plays into something that is in line with the common sense of jurors," Primus said. "It says, 'You can look with more skepticism at circumstantial evidence.'"

In the Flowers case, Hallmon's testimony helped the prosecution sidestep such skepticism.

Before Hallmon was allowed to take the stand as a state's witness, in Flowers' third trial, defense attorney Ray Charles Carter tried unsuccessfully to bar him from testifying. Carter argued that Hallmon was unreliable both as a jailhouse informant and as an admitted perjurer. After all, Hallmon had testified for the defense in Flowers' second trial and was now claiming to have lied.

"What it boils to," Carter said before the judge, "[is] that ... they are trying to take this case beyond circumstantial evidence. And they are so desperate to do it that they are willing to call a guy that has taken the witness stand and told a totally different story before."

But Judge Clarence Morgan sided with the prosecution. He allowed Hallmon to take the stand and ruled that "the testimony of Odell Hallmon would make this a direct evidence case." That would mean no special jury instructions and no special handling by an appellate court.

There's one other reason that Odell's testimony was so significant. Juries take confession evidence extremely seriously. Any allegation, no matter its source, that a defendant confessed is difficult for the defense to overcome.

"People have very strong intuitions that a person wouldn't confess to something he or she didn't do," Primus said.

According to a 1990 U.S. Supreme Court ruling, "A defendant's confession is like no other evidence. It is probably the most probative and damaging evidence that can be admitted against him ... a jury may be tempted to rely on it alone in reaching its decision."

Studies have shown that the persuasiveness of confession testimony holds even if jurors can tell that the confession was coerced by law enforcement. In the case of a "secondary confession" — meaning the confession was made to someone other than a cop — jurors tend not to be bothered if that someone is himself a criminal.

In the Flowers trials, Hallmon repeatedly swore that he hadn't been given anything in exchange for his testimony. So jurors didn't have to reckon with the question of how leniency offered for his own crimes might have affected his credibility.

Even so, they might not have cared. In an experiment a decade ago, University of Alabama psychologists presented mock jurors with transcripts from a trial with a confession witness. In some scenarios, the witness didn't say he had received a benefit for testifying. In others, he said he had — either money or a reduced sentence. The jurors' conviction rate was unchanged.

"Even though the witness ... had an enormous motivation to fabricate evidence ... jurors appeared to ignore this information and render verdicts that were not significantly different," Professor Jeffrey Neuschatz and his co-authors wrote in a 2007 paper.

It's clear that prosecutors in the Flowers case understood the potency of Hallmon's testimony. In closing arguments in Flowers' most recent trial, Evans' assistant district attorney Clyde Hill used Odell as his kicker.

After winding back through all the circumstantial details the state had presented, touting the "interlocking corroboration" of the route and the timeline and the ballistics, Hill arrived at Odell Hallmon. Judge Joseph Loper had already warned Hill that he'd run down the clock. But he had saved his best for last.

"Odell came and told you what Curtis said," Hill concluded. "Okay. My time is up."

As critical as Hallmon's testimony was to the prosecution, his recantation may be equally devastating.

Hallmon's on-the-record admission to "In the Dark" that what he said on the stand — from the fact that he'd been offered nothing in exchange for his testimony to Flowers' alleged confession — "was a lie" could lead an appeals court to throw out Flowers' conviction.

Flowers' lawyers have filed a post-conviction appeal on his behalf. One key question at this stage is whether there's new evidence that, had a jury heard it, might have changed the outcome of Flowers' last trial. It's possible that Hallmon's recantation will meet that standard.

If so, Doug Evans could face the prospect of trying Curtis Flowers a seventh time, without the aid of his key witness.

Odell Hallmon's first flip, from defense witness to state's witness, helped send Curtis Flowers to death row. His latest flip might just be the thing that gets Flowers out.