Mary "Missy" Anastasi told a Montgomery County jury yesterday that she believed from the day her 5-month-old son died that her ex-husband, Garrett Eldred Wilson, had killed him.

Testifying during the first-degree murder trial of Wilson, Anastasi said her questions about their son's death were based on Wilson's actions immediately after little Garrett Michael Wilson died in August 1987--the father spent much of the day playing video games and then moved the child's safety seat out of her car--and about the insurance policy he had purchased on their son.

"Garrett did this for the insurance money," Anastasi recalled telling her sister-in-law, Susan, at Shady Grove Adventist Hospital, hours after she found Garrett Michael limp in his crib.

The child's death was originally attributed to sudden infant death syndrome, the same cause of death attributed to another of Wilson's children in 1981. Both were changed to smothering after Anastasi contacted police about her suspicions in 1993.

Prosecutors have charged Wilson, 43, with smothering both children to garner a total of $190,000 in life insurance. Wilson is to be tried in Prince George's County in September in the 1981 death of his 2-month-old daughter, Brandi Jean.

Barry Helfand, Wilson's attorney, has argued that SIDS was the cause of Garrett Michael's death and that the later ruling of homicide by the state medical examiner was flawed and illegal. He also has argued that Anastasi was a scorned woman who was seeking revenge against her unfaithful ex-husband.

The third day of testimony was the first to focus on Garrett Michael's death. The first two were filled with testimony about the death of Brandi Jean, which Circuit Court Judge Ann Harrington has allowed because of what she ruled were similarities in the two deaths.

Anastasi told the Rockville court that her relationship with Wilson included an awareness of SIDS from the day she met Wilson in 1985. She said Wilson told her that he was divorced and that he had had a child whose death was attributed to SIDS, or "crib death."

They were married the next year, and during her pregnancy with Garrett Michael, she so feared her child would also succumb to SIDS that she sought genetic counseling, Anastasi testified.

After the baby's birth, Anastasi said, Wilson proposed buying a life insurance policy, but she felt "it wasn't something that normal people do." When he came home with a policy, she said, she put it in a closet where the couple kept all their business papers.

Anastasi told the court that in the predawn hours of Aug. 22, 1987, she heard the cries of her son in a nearby room. She started to get up, but, she said, was stopped by her husband, who for the first time said he would get up to feed the baby.

"I was surprised," she said. "He didn't even know what to do."

Anastasi testified that she heard the sound of a chair rocking through the baby monitor. Then she heard what sounded like her husband standing next to the baby's bed, then heard nothing for six or seven minutes, she said.

Suddenly, she heard "padding," then a sigh that "just made me nervous. I jumped up." But first she went downstairs to feed her two crying cats, Anastasi said. When she returned upstairs, she went into the baby's room and found the child limp.

Helfand's cross-examination focused on why Anastasi got up to feed the cats but didn't check on the baby immediately. He questioned why the cats were allowed to roam the house and suggested that the cats might have played a role in Garrett Michael's death.

Anastasi testified that she had been aware only of $10,000 in insurance money but that in the months after their son's death, her ex-husband showered her with expensive presents, including a diamond tennis bracelet, a new house and other jewelry.

CAPTION: Bed linens of Garrett Michael Wilson, right, are used as evidence in the trial of his father, Garrett Eldred Wilson, who is also accused of killing Brandi Jean, left.