ORLANDO, Fla. -- The day before the mother of a missing 3-year-old Orlando girl will officially be arraigned on murder charges, a veteran defense attorney said the evidence in the case is weak at best.

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IMAGES: Wild Ride In Orlando
IMAGES: Casey Anthony, Baez
VIDEO: Casey Anthony, Attorney Hold News Conference

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Casey Anthony will be arraigned on a first-degree murder charge in the disappearance of her 3-year-old daughter, Caylee, who was last seen in mid-June.

Anthony has already entered a written plea of not guilty, and is not required to be in court.

Attorney Diana Tennis said she is not sure the state's case against Anthony is solid.

'There's a big difference between interesting science evidence and evidence that actually gets to a jury," Tennis said.

Authorities on Friday released a report from a Tennessee lab that found five compounds consistent with body decomposition. Tests found evidence of decomposition on a hair strand found in the trunk, described as "microscopically similar" to one found on Caylee's hair brush.

"This whole talk about the 'body farm' and these interesting tests that this one organization is doing is very, very fascinating. It may be good information, but it's also possible that the jury is never going to hear about it," Tennis said.

Tennis cited the example of lie-detector tests, which law enforcement agencies consider credible but courts do not.

"No matter how good the science may be, that doesn't mean the judge is going to let the jury hear about it if it's not completely trustworthy," Tennis said.

Anthony Family Attends Ceremony

Meanwhile, Caylee's grandfather, George Anthony, said a ceremony held for missing children at Florida's Capitol was "gut-wrenching."

George and his wife, Cindy Anthony, joined 13 other families and Gov. Charlie Crist at the annual Missing Children's Day commemoration Monday. Cindy Anthony said the other families in attendance offered comfort and inspiration.

Cindy Anthony said her family continues to believe Caylee is alive.

A national search for Caylee continues.

Watch Local 6 News for more on this story.