OAKLAND -- In the weeks before Giselle Esteban is alleged to have murdered her former best friend, Michelle Le, she conducted numerous Internet searches seeking information that a prosecutor hopes prove that the killing was planned, evidence presented at trial revealed Monday.

Through questioning of an FBI computer forensics expert, deputy district attorney Butch Ford showed that Esteban, 28, sought information about, among other things, how to induce a heart attack, how to break into a locked door and how to follow someone without being noticed.

In addition, an analysis of Esteban's computer found that someone using her login information also made about 300 searches in about two weeks, seeking information about Le's residence.

Ford argued during opening statements that he will prove to a jury that Esteban planned to kill Le, 26, because she believed that the nursing student was having an affair with Esteban's former boyfriend and father of her daughter.

Meanwhile, Esteban's defense attorney, Andrea Auer, said the evidence will only prove that her client killed Le in a "heat of passion."

But the evidence presented Monday showed that Esteban began looking for ways to kill at least two weeks before she tracked down Le on May 27, 2011, in the parking garage of the Kaiser hospital in Hayward.

Jann Hayes, a senior computer forensic examiner with the FBI, testified that she was given Esteban's computer by the Hayward Police Department on May 31, 2011, and asked to conduct an analysis to find any information regarding Le or anything related to the case.

Hayes said her examination found "an overwhelming amount of data" pertinent to the case.

Among the searches Hayes said she found were, "How to break a deadbolt lock," "Chemicals that can induce heart attacks," "How to find someone who doesn't want to be found," and "How to follow someone without being caught."

Hayes said most of the searches were conducted between May 13 and May 27, 2011, the day Le went missing and the day authorities say Esteban killed Le in the parking garage.

In addition, Hayes said, she found evidence that someone using Esteban's login and computer searched Le's name "about 300 times" during that same time period.

Hayes was Ford's second-to-last witness before he completes his case against Esteban. Ford is scheduled to place a DNA expert on the witness stand Tuesday to discuss how police found Esteban's DNA in Le's car.

The defense is expected to begin its case once that testimony is completed.