From PEOPLE Magazine Click to enlarge
On the afternoon of June 16, 2008, the same day 2-year-old Caylee Anthony disappeared, a mystery user logged onto the Anthonys' computer. Between checking Casey Anthony's Facebook and MySpace accounts, the user googled "fool-proof suffication" and looked at websites about asphyxiation. "It's important evidence," says Capt. Angelo Nieves of Florida's Orange County Sheriff's office. But investigators failed to find the searches until more than a year after Anthony, now 26, was acquitted of killing Caylee.

How did investigators miss this search?

Although police had Anthony's hard drive for three years, they only checked the Internet history on one of the computer's two web browsers. "It was an oversight," says Nieves. Or as one investigator said, "We blew it."

Would this crucial evidence have convicted Casey?

It's hard to say. Although the user was logged in as Casey, the Internet search was done after George Anthony says his daughter left the house. "If you believe the search was done by Casey," says her defense attorney Jose Baez, "you can't accept the state's timeline of what happened that day." But Jeff Ashton, the prosecutor, told reporters, "It's just a shame we didn't have it. This would have put the accidental-death claim in serious question."

Can she be retried for murder?

Double jeopardy forbids a retrial. "It's over," says Florida legal analyst Bill Sheaffer. "She could confess, and there's nothing anyone could do about it."