Esteban, 28, is suspected of killing Le, a former friend whom she had attended high school with in San Diego. Le, a 26-year-old San Mateo resident, was studying nursing at Samuel Merritt University in Oakland at the time of her death.
FBI computer forensic examiner Jann Hayes testified that when she examined Esteban's computer shortly after Le went missing in May 2011, she found about 300 Internet searches for Le's name.
"It immediately became apparent there were a large number of instances of 'Michelle Le'" searches, Hayes said.
In addition, Hayes said, the computer showed that someone had researched ways of inducing a heart attack without leaving a trace, how to follow someone without being caught, and how to break locks, deadbolts and doors.
Other searches focused on potassium chloride, highly toxic gases and carbon monoxide.
Prosecutor Butch Ford alleged in his opening statement two weeks ago that Esteban killed Le out of "jealousy, hatred and rage" because she blamed Le for wrecking her relationship with her daughter's father, Scott Marasigan.
Marasigan testified that he dated Le for a month in 2003 but never had sex with her. He said his friendship with Le didn't interfere with his relationship with Esteban, with whom he had an off-and-on relationship before winning sole custody of their daughter and permanently splitting with her.
Le disappeared from Kaiser Permanente Medical Center in Hayward around 7 p.m. on May 27, 2011.
Ford said DNA evidence, videotapes and cellphone records support the theory that Esteban attacked Le in the parking lot at Kaiser and then drove Le's body to the remote area between Pleasanton and Sunol where it was found nearly four months later.
Defense attorney Andrea Auer said in her opening statement that Esteban did not plan to kill Le but instead snapped as a result of "extreme provocation and heat of passion."
Ford said he expects to finish presenting his case on Tuesday.