Boy, 5, Due to Testify in Sister’s Death : Crime: His videotaped statement is expected to be introduced in the murder trial of Steven Delgado.

A 5-year-old boy will testify that he watched Steven Delgado fatally beat his 11-month-old sister in his mother’s Santa Ana apartment, a prosecutor told jurors Wednesday.

The boy, Johnny Ortiz, was in a bed with his sister, Amanda, when Delgado threw her against a wall and beat her repeatedly with his fists, then hit the boy in the mouth, according to a videotaped statement the boy made to authorities last fall. The statement is expected to be introduced later in the trial.

Johnny Ortiz’s role as the sole eyewitness to Amanda’s death was disclosed as Delgado’s murder and assault trial opened here Wednesday in Superior Court.

Neither Deputy Dist. Atty. Robert C. Gannon Jr. nor police have suggested a motive for the killing. But the father, Manuel Ortiz, said he believed Delgado killed his daughter because he felt the child was interfering with Delgado’s romantic relationship with the mother, Elizabeth Ruiz. Ortiz and Ruiz had separated at the time of the killing.

In contrast, defense attorney Frederick L. McBride told jurors that Delgado was alone with both children, but evidence would show that he was not present when the murder occurred.

“During the most probable time of the children’s beating, Mr. Delgado was in Anaheim with (softball) teammates” after a game, McBride told jurors. Delgado later went to the Ruiz apartment on North Durant Street, he added..

McBride said his client will testify on his own behalf.

An autopsy found that injuries to the girl’s abdominal area were the primary cause of death. Two skull fractures and multiple chest bruises were also found, according to Gannon.

Gannon said Delgado and Ruiz, who worked together at Liberty Mutual Insurance in Santa Ana, have known each other since childhood and renewed their acquaintance five months before the child’s death. He said the two were romantically involved and that Delgado had a set of keys to the apartment.

Johnny Ortiz, who survived the attack, first told authorities “two bad men” entered the apartment and struck him, according to Santa Ana Policeman Michael D. Fuller. The officer reported that he could find no sign of forced entry into the apartment.

Last week, Superior Court Judge Ragnar R. Engebretsen denied a motion by the defense to exclude the child’s testimony. Delgado is also charged with willful cruelty toward the boy.

“The manner in which the testimony was given was so suggestive that the child’s memory was distorted by the interview,” McBride said Wednesday. He also suggested that the child might not know what actually occurred or is attempting to protect his mother.

McBride described the behavior of Ruiz as “contradictory and inconsistent”--a characterization with which Gannon agreed. The prosecutor said that Ruiz has changed her account of what actually happened on the night that her daughter was killed several times during the investigation.