A Forestville man was found guilty of first-degree murder and child abuse in Prince George's Circuit Court yesterday, for drowning his 11-year-old stepdaughter in a bathtub last July.

Prosecutors are seeking the death penalty for Eugene Coleman, 38, who was also found guilty of falsely imprisoning his 12-year-old stepdaughter. The two children lived with their mother and Coleman at 7606 Main La. at the time of the incident.

Both prosecuting and defense attorneys agreed on the essential facts: While Coleman's wife went to a job interview, her husband bound and gagged his 12-year-old stepdaughter and forced her to lie on a sleeping bag in the basement of the one-story rambler. Then he went upstairs and drowned the girl's sister, Leticia, in a bathtub.

But defense attorney Joseph Finlayson Jr. argued his client was not guilty by reason of insanity. The offenses were "horrendous, heinous," he told the jury, but Coleman did not know what he was doing at the time. He said Coleman had been depressed and reclusive after several years of unsuccessful job-hunting, and could not remember drowning his daughter.

But Prosecutor Margaret N. Nemetz argued that Coleman acted rationally and intentionally. Coleman was "doing something devious, or was attempting to do something devious," she said, and when Letecia Carson refused or objected, "she met her doom." It was "a loathsome plan, but a rational one," Nemetz concluded.

A county detective, Michael G. Ferritter, told jurors he interviewed Coleman shortly after the drowning and that Coleman told him, "I just killed my daughter. I'm sorry I did that. I hurt a lot of people."

Ferritter said Coleman told him that he held his stepdaughter "under the water until she was kicking and fighting. Then she stopped." Coleman then took the older sister upstairs and showed her what had happened, prosecutors said. When the girls' mother came home, the 12-year-old escaped and ran to the neighbors, who called the police.

Coleman, who has been held without bond, will be sentenced by Circuit Court Judge Howard S. Chasanow within two weeks, and, under Maryland law, must receive either the death penalty or life imprisonment.