Pedro Joaquin Olivas is being charged in the boy's May 8, 2004 death.
The boy's name was Fernando, and he was Olivas' child out of wedlock with another woman.
Olivas, who prosecutors say was married with three children, was baby-sitting Fernando on the night of the incident. It was allegedly only the second time that Olivas had been left alone with the child.
Later that evening, prosecutors say, Olivas called his girlfriend at work to report that their son had fallen out of bed twice. The couple rushed Fernando to the hospital, where he was later pronounced dead.
However, prosecutors saythat an autopsy revealed that Fernando's injuries were inconsistent with Olivas' story.
One year later, in June, 2005, a grand jury indicted Olivas on two counts: assaulting a child under 8 years old and murder.
The alleged crime was partly a result of Olivas' complicated marital situation, according to Deputy District Attorney Al Giannini.
"People don't just wake up in the morning and say, 'I'm going to kill a child,'" Giannini said. "These crimes always happen because of family dynamics."
Olivas told his girlfriend that he would divorce his wife for her, according to Giannini. His girlfriend, who reportedly referred to Olivas as her fiance, allegedly told Olivas that she would not engage in "relations" with him until he divorced.
"I can assure you there is another perspective, without a doubt," said defense attorney Scott Furstman.
Although he declined to comment further on the case prior to trial, Furstman said Fernando's death "resulted from an accident in an unfortunate sequence of events."
Prosecutors contend that Olivas claimed that Fernando's injuries resulted from a drop onto a carpeted surface and a second fall which resulted in the child hitting his head against the wall.
The District Attorney's Office spent more than a year investigating the child's injuries prior to calling a grand jury "in order to be absolutely sure that there was not a possibility that this was, in fact, an accidental death," according to Giannini.
The jury trial, which the attorneys estimate will last three to four weeks, is scheduled to begin today with jury selection.
A Superior Court judge began hearings on trial motions last week, accepting a prosecution motion to admit photographs of Fernando's injuries and a defense motion to exclude evidence of Olivas' prior theft and acts of road rage. Meanwhile, the judge denied a defense motion to preclude the use of language such as "shaken baby syndrome."
Olivas has remained in custody, in lieu of $3 million bail, since his 2005 arrest.
Staff writer Michael Manekin can be reached at (650) 348-4331 or by e-mail at firstname.lastname@example.org.