The case against Wayne Bertram Williams, accused of committing two of the murders that terrorized Atlanta for two years, is a "jigsaw puzzle with a whole lot of pieces," prosecutors said today.

"You'll have to be like investigators seeking out the truth," Fulton County District Attorney Lewis Slaton told the jury. But he only hinted at circumstantial and fiber evidence allegedly linking Williams, a freelance cameraman and self-styled talent scout, to the killings of two of the older victims in the 28 murders of young blacks that baffled law enforcement officers and kept the city on edge from July, 1979, to May, 1981.

"The evidence that ties the defendant to the murders will come out later in the trial," he said, urging the jury to "sit back and enjoy yourself. Stay alert. We'll try to make it as interesting as possible."

Williams is accused of strangling Nathaniel Cater, 27, and asphyxiating Jimmy Ray Payne, 21, and dumping their bodies in the Chattahoochee River.

But defense lawyers portrayed their client as a brainy child and a "free spirit with proud parents" who got too much love and attention to grow up to be a killer. His father bought him a set of model trains at 3. He won a science award in the third grade. He was an honor student. He started a radio station in his basement.

"You don't get a killer when you get a boy who was raised like this boy was," drawled attorney Alvin Binder. He said the only thing that Wayne Williams ever killed was a roach in his cell while waiting for his day in court.

Binder said it was hard to imagine how his client could have hoisted the larger and stronger victims over a four-foot bridge railing and into the river. "He could be in a little better physical shape," Binder said of the pudgy Williams.

The line brought a grin from Williams, who sat through most of the day hunched over and stone-faced. His mother and father, Homer and Fay Williams, both retired schoolteachers, sat one row behind.

Payne's girlfriend, Kathleen Turner, testified she last saw Jimmy Ray at 8 a.m. last April 21, as he left the rundown apartment they shared for the Omni Coliseum downtown. Slaton held up a pair of red undershorts found on the body pulled from the river April 27. Turner identified them as Jimmy Ray's.

Payne's mother, Ruby Jones, testified that her son never swam in the river, only in the park. She bit her lip as she described how Payne had served time in prison. Neither Jones nor Turner said they had ever seen Williams or heard Jimmy Ray mention his name.

"Ever see him Williams before today?" Binder asked.

"Only on TV," said Jones.

Binder attacked the victims, trying to separate them from the Norman Rockwell portrait he painted of Williams. Life had not been good to Nathaniel Cater, he said. "He was known as 'street-wise.' He drank excessively. He sold his blood for money. He sold his body." He portrayed Payne as an ex-con who attempted suicide twice.

Williams was stopped early last May 22 as he drove over a bridge on the Chatahoochee River moments after an officer on stake-out heard a splash. Two days later, Cater's naked body was pulled from a spot downstream. Bodies began turning up in area rivers after an article detailing fiber evidence found on the victims appeared in the Atlanta Constitution, Public Safety Commissioner Lee Brown testified.

Those fibers are believed to hold the key to the prosecution's case against Williams. Slaton is expected to try to convince the jury that fibers and dog hairs taken from Williams' bedspread, carpet, car and dog match those found on the two victims, proving he came into contact with them.

A veteran prosecutor with a nasal voice and deliberate manner, Slaton dealt his hand slowly, calling the first nine of a possible 544 witnesses, laying the groundwork, introducing two fishermen who found Payne's body, then calling a medical examiner who testified that Payne was asphyxiated.

But Binder, a shaggy Mississippi lawyer with a sleepy style, tried to take the wind out of the prosecution case early as he chronicled Williams' life, from birth to arrest, raising questions about the investigation and the circumstantial evidence against his client.

He even suggested that Williams may have been railroaded after high officials in Washington, D.C., "north of the Mason-Dixon Line," dispatched federal aid to Atlanta to solve the killings.

"The evidence will show no one ever saw him throw anything off the bridge," he said. Williams was out at 2:50 a.m. May 22, trying to hunt up an address, he said. He was out at that hour because the family had one car and it was the only time he could use it for his work.

Binder tore into the alleged fiber evidence against his client before it was even presented. "This type evidence cannot prove a person was definitely in contact with another person at a specific time," he said. "You see if the experts don't say that."

What one expert did say was that Payne did not drown; he was asphyxiated. Dr. Saleh Zaki, the associate Fulton County medical examiner who performed the autopsy, testified that he changed his initial finding June 16 of cause of death unknown to homicide on Aug. 6, after he learned more about the victim.

Payne's body was a mystery, Zaki testified. He found water and mud in the nose and mouth, but no water in the sinuses or lungs. There were no marks about the neck, as one might find in a strangling or choking.

But there were bruises on the forehead, one leg and a shoulder. Zaki found a wad of chewing gum stuck in a molar. There were no puncture marks, no bleeding. The body, he guessed, had been in the water between five and seven days.

In the first major skirmish, Binder badgered the British-trained pathologist over why he changed the autopsy report. "You can't rule out drowning, can you? You couldn't say he wasn't alive when he entered the water, could you?"

Drowning could not be absolutely ruled out, Zaki conceded. But he said it was highly unlikely based on the information he later learned about Payne with help from task force investigators.

Zaki said he asked himself a few questions. "Is Mr. Payne a frequent visitor to the Chatahoochee River? Does he have friends near there? Does he like to swim in the river ?" The answers were no in all cases.