For weeks, Casey Anthony sat at her murder trial with her defense team anxiously waiting for prosecutors to drop a bombshell: computer evidence, the state would argue, showing Anthony researched how to kill with poison and suffocation on the same afternoon her daughter, Caylee, was killed by poison and suffocation.

But the bombshell never exploded.

"We were waiting for the state to bring it up," defense attorney Jose Baez told WKMG-TV in Orlando, Local 10's sister station. "And when they didn't, we were kind of shocked."

Baez first revealed the evidence in his book, "Presumed Guilty," but blamed Anthony’s father, George Anthony, for the computer activity. Baez suggested George Anthony was considering suicide after Caylee accidentally drowned in the family swimming pool.

But an investigation has uncovered evidence indicating it was most likely Casey doing the search.

And, in a stunning lapse, prosecutors -- relying on woefully incomplete information from the Orange County Sheriff's Office -- never even saw the potentially damning computer browser evidence, until Local 6 revealed it to them last week.

How damning is it?

Consider what they appear to show happening online the afternoon of Monday, June 16, 2008, the day Caylee died:

  • At 2:49 p.m., after George Anthony said he had left for work and while Casey Anthony’s cellphone is pinging a tower nearest the home, the Anthony family's desktop computer is activated by someone using a password-protected account Casey Anthony used;
  • At 2:51 p.m., on a browser primarily Casey Anthony used, a Google search for the term "fool-proof suffocation," misspelling the last word as "suffication";
  • Five seconds later, the user clicks on an article that criticizes pro-suicide websites that include advice on "foolproof" ways to die. "Poison yourself and then follow it up with suffocation" by placing "a plastic bag over the head," the writer quotes others as advising;
  • At 2:52 p.m., the browser records activity on MySpace, a website Casey Anthony used frequently and George Anthony did not.

"I really believed that (prosecutors) were going to sandbag us with it," said Baez.

After all, poison, suffocation and plastic bags were exactly what the state claimed Casey Anthony used to murder Caylee and dispose of her body; poisoning her with chloroform, suffocating her with duct tape, then placing her body in two plastic bags.

After our sister station described the findings earlier this month, trial prosecutor Jeff Ashton said, "It's just a shame we didn't have it. This certainly would have put the accidental death claim in serious question."

Ashton retired after the trial, wrote a book on the case and, in January, will become state attorney, unseating his former boss in this year's election.

Who's to blame

With an army of investigators and prosecutors spending three years, hundreds of thousands of dollars and untold man hours on the most notorious, high-profile murder case in Florida history, the blame for overlooking key evidence could be placed at many feet.

"I don't think it's appropriate for me to say this person messed up, that person messed up or we messed up," said Ashton.

The Orange County Sheriff’s Office, which possessed the evidence but failed to extract it and turn it over to prosecutors, now realizes what it missed.

“There was an oversight,” said sheriff’s Capt. Angelo Nieves, confirming that the agency tried and failed to extract information that would have revealed the entire Internet browsing history for that day. “This has been a learning experience for investigators as well.”

Both Ashton and the lead prosecutor, Linda Drane Burdick, noted that prosecutors asked the Sheriff's Office to produce an Internet history of the computer for June 16, 2008.

But the request came relatively late, less than two months before trial, after prosecutors learned from defense witnesses that Casey Anthony was going to claim she was awakened that morning by her frantic father looking for a missing Caylee.

In an April 5, 2011, email to sheriff's computer examiner Sandra Osborne, Burdick wrote, "I believe, based on your reports, that we can disprove” Casey Anthony’s claim that she was awakened by her father when Caylee disappeared. They could do that, Burdick wrote, “by demonstrating (if possible) what was actually happening (I guess that means user activity and Internet history) on the computer during the time frame."

In response, lead sheriff's Investigator Yuri Melich sent Burdick a spreadsheet that, our investigation found, contained less than 2 percent of the computer’s Internet activity that day.

Melich and Osborne relied on Internet data from the computer’s Internet Explorer browser – one Casey Anthony apparently stopped using months earlier. Since March, she preferred the computer’s Mozilla Firefox browser, as investigators already knew.

The spreadsheet sent to Burdick included 17 vague entries from the Internet Explorer browser history on June 16, 2008, and failed to list 1,247 entries recorded on the Mozilla Firefox browser that day -- including the search for “foolproof suffocation.”

The mistake meant prosecutors went to trial unaware of 98.7 percent of the browser history records created that day.