A D.C. police officer was convicted yesterday of numerous charges involving family violence, including separate incidents in which prosecutors said he kicked his wife, beat his stepson and killed the family's two pet cats.

Kenneth L. Nelson, 34, showed little reaction as D.C. Superior Court Judge Lee Satterfield found him guilty of assault, cruelty to animals and other misdemeanor charges. Satterfield, who presided over a week-long non-jury trial, ordered the officer jailed immediately. Satterfield convicted him of 19 counts and acquitted him of a dozen others.

Nelson has been on administrative leave since April 1998, when he was arrested at the 3rd District headquarters, where he worked. He could face up to 9 1/2 years in prison when Satterfield sentences him Sept. 21. During the trial, he repeatedly denied wrongdoing and said the allegations were lies. Police internal affairs investigators attended the trial.

Assistant U.S. Attorneys Amy Salvin and John Cummings contended that Nelson's abuse of his wife, stepchildren and pets unfolded over a two-year period that began in 1996. The youngsters, a boy and a girl who are 9-year-old twins, were among the witnesses who chronicled a sad, tumultuous history. Satterfield said their testimony convinced him that the violence took place. Nelson's wife, Delores Grady, 33, eventually divorced him and moved away with the children.

Many of the incidents took place in an apartment in the 6600 block of Georgia Avenue NW, the prosecutors said. They included instances in which Nelson allegedly choked, kicked and beat his wife. In one episode in March 1998, she said, he allegedly pointed his police weapon at her, handed her a second gun and suggested the two shoot each other to death. The next month, she said, he beat his stepson with an electrical cord. Weeks later, he allegedly threatened his wife with a knife and hung a noose.

The first cat died in early 1997, prosecutors said. Nelson's stepdaughter said she saw him take Tigger into a bathroom and heard what sounded like a beating. Prosecutors said he later buried the pet in a shoe box.

Tigger was replaced by another cat named Frisky, prosecutors said. The family members said they watched Nelson choke that pet to death, in the spring of 1997, when he was supposed to be giving the cat a bath.

Prosecutors said Nelson's wife got a court order in May 1998 requiring him to stay away from the family. Nelson was convicted yesterday of repeatedly violating that order by either calling or visiting the house.

Defense attorney Thomas Heslep urged Satterfield to permit Nelson to remain free, saying that Nelson has been treated for alcohol abuse and psychiatric problems. But Satterfield turned down the request, saying, "The court does not believe his mental health had anything to do with his conduct."