Revelations about the sinister searches made from the Anthony family's home computers show that someone visited a site on how to make chloroform 84 times.
Three computer forensic analysts testified that someone in the Anthony family home in March of 2008 made numerous searches for things like "death," "how to make chloroform" and "self defense." That's more than three months before Caylee was reported missing.
The trunk of Casey Anthony's car tested for high levels of chloroform and for human decomposition.
Detective Sandra Osborne from the Orange County Sheriff's Office said that the searches had been deleted by the user, but had not been overwritten so she was able to access them.
A desktop computer, a laptop, two digital cameras and Casey Anthony's cell phone were also analyzed. There was no Zenaida Fernandez Gonzalez found in Casey Anthony's cell phone record, forensic analysts testified.
When authorities were first alerted that Caylee was missing on July 15, 2008, Anthony claimed a nanny named Zenaida Fernandez Gonzalez had taken her.
Analysis of the computers showed no searches or reference to Zenaida Fernandez Gonzalez until July 16, 2008. That is the same day that Casey Anthony was arrested after she lied to police about where the fictional babysitter lived. She took police to various addresses including an apartment that hadn't had tenants in months.
"This has been the worst day yet for the defense and the best day for the prosecution in proving premeditated murder," said Dan Abrams, ABC News' legal analyst. "The defense's best hope has always been this idea of an accident…This is why these computer searches become so important because this undermines that entire defense of an accident."
Casey Anthony's defense attorney Jose Baez argued that no one could say with certainty who made those searches.
One computer analyst testified that the searches were done under a login called "Casey" and with a password that included part of a boyfriend's name.
Baez also challenged the experts, asking one witness how much he was getting paid for his analysis.
If convicted of the most serious charge, Casey Anthony could face the death penalty.
ABC News' Ashleigh Banfield contributed to this report. Affiliate WFTV contributed to this report.
Watch "20/20" Friday at 10 p.m. ET for more on Casey Anthony's story.