One morning in October 1976, while 19-year-old Annette Nee was studying for her midterm examinations at the University of Maryland, a man pushed his way inside her Hyattsville apartment and demanded her pocketbook. When she refused to give it to him, the man shoved a gun in her face and killed her.

That much witnesses in the murder trial now going on in Prince George's County Circuit Court agree on. What the jury will have to decide is who fired the gun that killed Nee and sent her father on a five-year search for clues to the slaying.

The prosecution contends that the man who killed Nee is the defendant, George D. Robinson, 30, of Northwest Washington. But Robinson's lawyer, Richard Sothoron, told the jury yesterday that his client is innocent and that the man who actually killed Annette Neen is Robinson's former partner, James Settles Jr., 29, an inmate at St. Elizabeths Hospital who has testified against Robinson.

For four days Nee's mother, Sugi, has been in the courtroom listening to testimony in the case, which could go to the jury today. But because he appeared as a witness, Nicholas Nee, who found his daughter's body and then became obsessed with a search for clues, has had to wait outside.

In the years after his daughter was found dead, Nicholas Nee wrote hundreds of letters to her friends pleading for information that might help him understand why she was slain. When no clues were forthcoming, he took out 20 newspaper ads in which he offered a $10,000 reward for information leading to the arrest and conviction of the killer.

The reward money alternately appeared as a blessing and a curse in the case. One of the key witnesses, Settles, has admitted that it might have been the reward money that led him to tell police about the killing -- a fact that the defense has used to cast doubt upon his testimony -- while the prosecution has demonstrated that it was only one of several reasons prompting Settles to come forward with his information.

The three key witnesses in the prosecution's case have testified that Robinson told them he killed Nee. One of them, Settles, says that he drove Robinson to Nee's apartment on Oglethorpe Street the morning Nee was killed. Settles says he remained in the car when Robinson went into the building.

"I heard a shot," Settles testified. "Mr. Robinson came out of the apartment with the pocketbook underneath his shirt. I asked him what happened with that shot. He said he shot a young lady."

Another witness, Beckton Norfleet, who testified yesterday, says that Robinson confided in him in four different conversations during 1977 and 1978 that he had killed Nee. Three of the conversations took place in the federal penitentiary in Ashland, Ky., and one took place in the D.C. jail.

According to the state's attorney's office, Norfleet, now serving a prison term for robbery in Virginia, will get a $5,000 reward from Nicholas Nee for the information he provided police.