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Good Question: When Is The Evidence Good Enough?

MINNEAPOLIS (WCCO) -- Prosecutors in Florida had a pile of circumstantial evidence that led many to believe that Casey Anthony was guilty of killing her 2-year-old daughter Caylee. However, a jury found her not guilty. So, what kind of evidence is enough?

"She didn't report her daughter missing for a month. That's the strongest evidence against her," said Stephen Simon, a professor at the University of Minnesota School of Law.

But there was no direct evidence: no eyewitness, no confession. Also, there was no real physical circumstantial evidence: no DNA, no fingerprints.

"Circumstantial evidence cases are hard. They require more evidence, they require better evidence because you have to anticipate," said Simon.

It seems like nearly every big-time trial is full of circumstantial evidence, and that's not because most cases that are charged are circumstantial.

"About 85 to 87 percent of the cases are resolved by plea, which means, OK, you got the evidence," said Hennepin County Attorney Mike Freeman.

"The cases we end up trying are the ones with the longest sentences and the ones with the most circumstantial evidence," he said, because the ones with the solid, direct evidence end up with plea deals.

According to Freeman, about 65 percent of cases have confessions, so there is direct evidence in those cases.

So, how is a jury to sort things out in a trial with circumstantial evidence?

Some types of circumstantial evidence carry more weight, "Things like a fingerprint, DNA, something that is very, very unique," said Simon.

"If we have DNA, we don't usually have a lot of trouble," echoed Freeman.

So, conviction can be very difficult without unique physical circumstantial evidence.

"The juries are anguishing over their job. They're so concerned they're making the right decision," Simon explained.

And the expectation for direct evidence has gone up, according to Freeman.

"Juries say: Where's DNA? Where's blood? Where's the handwriting analysis? They want that. We work hard to come up with that, because that's what they're expecting," he said.

For a juror, they have to reach one of the highest standards for conviction in the western world: guilty beyond a reasonable doubt.

"The jury did their job," said Simon. "You can't convict this person because she's not a nice mom."

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