Testimony a game-changer in Amanda Knox's favor?

Testimony in Amanda Knox's appeal of her murder conviction in Italy may be a game-changer in favor of the college student from Seattle, an expert and Knox's sister say, and her sister says it left her thinking Amanda would be coming home soon.

Knox, now 23, and ex-boyfriend Raffaele Sollecito were convicted last year of murder and sexual assault in the 2007 death of Briton Meredith Kercher, with whom Knox shared a cottage in Perugia while attending college. Knox and Sollecito were sentenced to 26 and 25 years in prison, respectively.

Knox and Sollecito have always denied wrongdoing, insisting they weren't at the cottage the night Kercher was killed, but were at Sollecito's house.

On Saturday, key prosecution eyewitness, Antonio Curatolo, who'd said he saw Knox near the crime scene the night of the murder, admitted to heroin addiction and confused crucial details from the night of the murder, including dates.

"He basically blew the whole prosecution's case right then and there," Knox's sister, Deanna Knox, told "Early Show" co-anchor Chris Wragge. "He got his dates mixed up. He said he was on drugs at the time. He was recalling that people were in costumes on Halloween, which was actually the day after. So he pretty much blew every credibility that he had."

Asked if that was a game-changer, Deanna replied, "Yeah, it really was. It was one of those moments for me where I was like, 'Wow, my sister could really be out soon!' Which is really exciting. And I know our lawyers were happy. And our family was happy."

Deanna conceded that Amanda is "still really nervous about the appeals process. She thought that she should have been out the first time (at the conclusion of her trial). So she's a little nervous still, that they're not gonna to get it quite right. But she seems confident. She's confident in her innocence, and she was just really happy to see her family. So it was nice to see her that way."

CBS News legal analyst Jack concurred that the testimony could be a game-changer, pointing out, "You've got to remember the system is very different over there. Her appeal is essentially a second trial, new jurors, new judges, and the conviction was based on circumstantial evidence. You know, direct evidence is either you confess to a crime or somebody says, 'I saw them committing the killing.' Circumstantial is bits and pieces that you put together to form a picture. And here, the first time around, the picture was enough for her to be convicted. But they're starting to chip away at that picture here. And significantly."

Curatolo, Wragge noted, has been a key witness in a number of different murder trials. "It looks like he's been kind of there for the prosecution on a number of different times. How did they not know that he would..."

"That's a tough question to answer," Ford said, "because ... this time around, they've challenged him that he had the wrong date, he had wrong details, and admitted to being a heroin addict at the time. You know what? As a prosecutor, I had to rely on some pretty shaky witnesses sometimes. I don't think I ever had somebody such as this.

"When you take away a so-called eyewitness like that, that's a significant loss for the prosecution."

Ford also observed that, "The court ordered that (new forensic tests on evidence) be done by independent experts. Not by the prosecutors or defense. And (those experts reportedly) raising questions whether there's even nearly enough evidence, DNA evidence on this knife blade (that was the alleged murder weapon) to point to Amanda Knox. ... If you pull that out of the case, if you pull the eyewitness out of the case -- or at least raise significant questions about the two of them -- you've put them in a situation now where Amanda Knox -- if I'm her attorney, I'm a lot more confident now that she might be coming home."