Giselle Esteban Convicted of Murdering Former Close Friend Michelle Le

By Howard Breuer

10/30/2012 at 04:30 PM EDT

Michelle Le

Hayward Police Department/AP

Giselle Esteban was convicted Monday of murdering Michelle Le – a woman who had once been her close friend, but who Esteban came to view as a romantic rival.

Esteban, 28, and Le were once classmates at Mount Carmel High School in San Diego, and later lived near each other in the San Francisco area. But according to trial testimony, that friendship soured when Esteban became convinced that her friend and Esteban's ex-boyfriend, Scott Marasigan, were romantically involved, that he got her pregnant in 2005, and that Le was responsible for the couple's breakup. (Marasigan testified that he and Le dated in 2003 for a month, but never slept together.)

Le, a 26-year-old nursing student, went missing from a hospital parking lot in Hayward, Calif., in May 2011. Her remains were discovered in September 2011 in the remote Sunol Canyon.

In closing arguments, Alameda County Deputy District Attorney Butch Ford argued that Esteban, of Union City, Calif., spent months planning her attack on Le.

"Sociopath, that's what we have here; she's laughing as she is talking about killing people," Ford said as he replayed a recording between Esteban and Marasigan six months before the slaying. "This is a planned assault, a strategic assault on someone who never saw it coming."

In the recording, Esteban tells Marasigan, the father of her 6-year-old daughter, "You deserve to die for your lies, as does she."

An FBI computer expert testified during the trial that Esteban ran about 300 searches for Le's name – and researched such subjects as inducing a heart attack without leaving a trace, following someone without being caught, how to break locks, deadbolts and doors, and highly toxic gases such as potassium chloride and carbon monoxide.

Giselle Esteban

Hayward Police Department / AP

Esteban's lawyer, Andrea Auer, didn't dispute that Le was an "innocent victim in this case" or that her client was responsible. But she said Esteban acted in the heat of passion and should be convicted of voluntary manslaughter.

The jury of six men and six women spent about a week deliberating. When the verdict came in late Monday, Le's family members held hands in the front row as the jury entered the courtroom.

"We were just hoping and praying the jury would make the right call, and this is it," Le's brother, Michael Le, told the Oakland Tribune . "We feel that a tremendous burden has been lifted."