A 24-year-old Hyattsville woman went on trial in Prince George's County yesterday for allegedly raping an 8-year-old boy.

The woman, Mary Augusta Conteh, allegedly forced the boy to have sex with her in her apartment while she was babysitting for him on May 2, assistant state's attorney Margaret Nemetz told a Circuit Court jury yesterday.

But Conteh denies that the incident ever happened, defense attorney Fred Joseph told the jury in his opening argument. "I suggest to you that what comes out of that little boy's mouth is not the truth," said Joseph.

Conteh, who is married and was five months pregnant at the time of the alleged incident, came to the United States five years ago from Sierra Leone to go to beauty school. She frequently worked as a babysitter, without pay, for friends in Hyattsville who also emigrated from Sierra Leone.

Conteh was arrested and charged with second degree rape, sexual assault and child abuse after the boy, whose nickname is "Junior," told his mother about the alleged incident. The boy did not tell his mother until three days afterwards, Joseph told the jury, and his mother did not phone police until three days after he told her.

Although court documents show that at one time defense attorney Joseph had considered disputing whether an 8-year-old boy can have sex, Joseph said yesterday that he does not plan to call physicians to testify on the subject.

There is no physical evidence in the case, which mostly comes down to the 8-year-old's word against Conteh's. Joseph told the jury he plans to present character witnesses "to show you why Mrs. Conteh could not have done what she's accused of doing."

Conteh sat next to Joseph at a table in the courtroom yesterday, listening attentively to the proceedings. Her hair was in braids; she wore a pink turtleneck shirt and a pink and blue plaid skirt.

Joseph and other sources said it was the first time in Maryland, and possibly in the United States, that a woman had gone to trial on a rape charge.

Before the case went to trial, Joseph tried to have the case thrown out on the grounds that the rape statute specifically applies to men raping women. But a judge ruled that the statute could apply to either sex.

The 8-year-old boy is expected to take the stand this week.