A 20-year-old student who stabbed his father, a NASA physicist, to death, was given a 10-year suspended sentence yesterday, placed on 5 years probation and ordered to spend 800 hours teaching reading, writing and arithmetic to inmates at the Prince George's County jail.

Circuit Judge Vincent J. Femia told David A. Chi, who was an honors student at Cornell University when he killed his father last June 19, that no good would come from sending him to prison. But society would be served, Femia said, by making Chi teach primary education in the jail, where "some poor unfortunate slob can profit from Mr. Andrew Chi's tragedy." Chi had already given Femia an outline of the classes he intends to teach.

Chi, who pleaded guilty earlier this month to second-degree murder, told Femia he did not know why he killed his father Andrew, 61, as Andrew Chi sat in a rocking chair at the family's home in Camp Springs.

"I really can't answer why," David Chi said. "I don't see any reason myself. I can't give an excuse or an explanation." Chi said, however, that he hoped "in some way that I can make it up to the community, and in some personal way to my father."

Femia told Chi that patricide has long been considered the most serious of crimes. "No matter how psychologically brutal your father may have appeared . . . he had the right to live," Femia said.

Chi's mother, Louisa Chi, told Femia in court that her husband, a NASA physicist for 18 years, dominated the family. "We lived under enormous pressure," she said. When her husband came home from work, "something came over us; he was so dominating it became frightening."

Her husband was never violent toward her or her son, she said, but they lived in fear. Her husband once hurled the family dog across the room, breaking its leg, she said. Sometimes her husband complained that family conversations "were not intellectual enough." When he was angry with her, she said, he would sometimes punish her by taking her car keys and witholding her household money.

The younger Chi, who was majoring in architecture at Cornell, was arrested the night of the murder, and released on bond the next day.