BELA CRKVA, Yugoslavia -- The case against Slobodan Milosevic hinges, in the end, on the particulars. That's why it is important that Zenel Popaj was wearing only his pajamas in the early morning of March 25.

Serb troops that night had rounded up as many residents of this village as they could find and lined the men up along the bank of a stream. Then the soldiers had shot them all with automatics. Forty-eight died. Before dawn broke, 15 people were killed elsewhere in the village. Two died later from their wounds.

The massacre led to one of seven counts in the indictment of Milosevic and four other top Serbian officials by the International Criminal Tribunal for the Former Yugoslavia. Testimony will come from the few survivors. Among them: the 58-year-old Popaj.

In the ruins of what used to be his house here, he described yesterday what it had been like during that night of confusion and terror.

He talked about standing in the dark alongside his 80-year-old father and not far from his 12-year-old nephew, both of whom died from the Serbs' bullets. He talked about his escape, crawling low through the bloody stream. And he talked about the bodies.

This weekend, forensic investigators from the war crimes tribunal will begin fanning out, to Bela Crkva and throughout Kosovo, to collect evidence of crimes like the one committed here.

"There is a very long list of sites we are interested in," Paul Risley, a spokesman for the tribunal, said yesterday. NATO troops and others, he said, have found evidence of so many apparent war crimes in Kosovo that what was planned as a seven-day forensic program will inevitably last much longer.

In addition to murder, he said, the potential crimes include illegal detention, torture, deportation and military attacks on civilian villages. But murder is the easiest to ascertain, particularly when the bodies are still in place.

One place the investigators will be sure to look is Bela Crkva.

Villagers buried their dead after the Serbs left, but the graves are only a few yards from where the little stream curves under a railroad bridge, at a place called Ura Belajes.

Bela Crkva (the name is Serbian, and it means White Church) was an entirely Albanian farming village when the Serb police came in March. It lies on flat land in the west, within sight of hulking Mount Pashtrik, beyond which lies Albania.

About 3,000 people lived here, and they had had trouble with police before. On July 18 and Sept. 2, police had descended on the village and given everyone a scare. On another occasion, officers shot up a car driving down a farm lane nearby, killing three of the four occupants.

Villagers begin to flee

On March 22, the possibility of a NATO bombardment of Yugoslavia had become very real, and people began to flee Bela Crkva when police set up a post outside town. More people fled the next day and the next, but some of them began to drift back when they saw that police were leaving the village alone.

That's why no one knows quite how many people were in Bela Crkva when the Serbian forces struck.

Popaj thinks there were about 300. He was one of them. He had gone to bed, in his pajamas, when the NATO bombardment began in the early morning of March 25.

"They came to the village at 3 o'clock in the morning," he said.

Among them were Yugoslav soldiers, paramilitaries and special police units, according to Teki Zhuniqi, another villager who was there that night but avoided the massacre scene.

The townspeople fled into the fields southwest of Bela Crkva, but after a half-hour some, including Popaj, headed back to their homes.

"That's when they started setting fire to the houses, and the tanks began approaching from the hills," he said.

At this point everyone headed back into the fields, toward the bridge at Ura Belajes.

"Then someone looked back and saw the police coming," he said.

They kept walking, trying not to panic, but they saw more police coming from both sides.

Assailants wore masks

They came upon two families -- 13 people -- one family from Bela Crkva, the other family refugees who had moved to the village. The villagers moved past them and a short while later heard shots.

They reached the railroad tracks about a half-mile south of the village, and split into two groups. One tried to head toward the village of Zrze, and the other moved up the stream toward the village of Rugova.

"But there were snipers, and we didn't dare continue," Popaj said. "We came back, and they surrounded us. One of them, who spoke Albanian, said, 'Come and surrender. We are for peace.' We raised our hands, and they collected us all together."

Police, according to Popaj, Zhuniqi and other villagers who were there, then separated the women and children from the men and told them to head for Zrze.

An Islamic pilgrim, Biljal Zhuniqi, and another elder, Hysni Fatoshi, told police that they would vouch that the village men were not members of the rebel Kosovo Liberation Army. The police commander told them, this time in Serbian, to form a line.

They told the men to undress. Popaj, wearing only pajamas, was told to roll up his pants legs. The Serbs took all the money, jewelry and expensive watches they could find. Then, Popaj said, they took the men's documents and tore them up.

"You won't need these anymore," the men were told.

The police were wearing sunglasses and black ski masks, or else they had covered their faces with camouflage paint. They had white ribbons on their epaulets. One said to Popaj as he stood there, "Let Bill Clinton and NATO come help you now."

One man in the group, an X-ray technician named Mesim Popaj, said to the police, "How can I be a terrorist when only yesterday I was working with Serbian doctors?"

One of the policemen ordered the technician to walk down the bank into the stream, and then he shot him.

The rest of the men were ordered to get dressed again and told they would have to cross the stream. But Zenel Popaj had only to fling on his pajama tops and he was ahead of the other men -- though still short of the stream -- when the shooting began.

"As soon as I heard the shots, I jumped into the water," he said.

'The smell of blood'

Bodies fell all around him and on top of him. An officer with a pistol walked along the row of men, shooting anyone who appeared to be alive. Popaj lay hidden under the corpses, his face barely out of the water.

"I stayed there about 15 or 20 minutes," he said. "But I couldn't stand the smell of blood."

He walked on his hands and knees along the bottom of the shallow stream, went under the bridge and on the other side saw a petrified Shukri Gashi. The 16-year-old merely pointed when Popaj asked him where the police were, but he realized they had gone.

Popaj said he tried to give some first aid to the wounded -- 11 had survived, four unhurt and seven injured, though two of those died later from their wounds. But then he and another man headed for the nearest house.

On the way they came across the bodies of the two families they had passed earlier. All were dead except for a 2-year-old boy, who was crying for his mother.

They took him to the river, washed him and brought him to the nearest house, which was not burning. They bundled him in blankets and left him there, heading for the village of Celina, but when they heard shots they turned around and went to Zrze. They met the toddler's uncle there and sent him back to fetch the boy.

Teki Zhuniqi, who had fled across the railroad tracks and was hiding on the far side of the embankment, didn't see the shooting, although he heard it. He said he emerged the next day and late that evening began to help pull bodies out of the stream. There were 48. All that night he and other men buried them nearby, even as snipers fired on them from a grain elevator a half-mile or so to the west and from hills to the north.

Later, the villagers discovered three bodies in the village -- of a paralyzed man, a man whose leg had been amputated and that man's wife.

Zhuniqi and other villagers maintain that there was nothing to justify the massacre by the Serbs, that there were no KLA fighters in Bela Crkva. But Popaj's cousin, Sinan Popaj, acknowledged that he and three other armed KLA soldiers were just outside the village and eluded police by hiding in a dugout beneath the railroad tracks.

All the survivors left for Albania, with the exception of Zenel Popaj, who moved from village to village in Kosovo while the war went on.

The Serbs destroyed Bela Crkva. Every house is burned and smashed. Everything of value has been taken. The mosque is wrecked, the minaret toppled. Yesterday, mourning doves were cooing on its empty windowsills.

Nothing left

In the past two days, 100 villagers have returned, camping in the blackened remains of their homes. They say they'll rebuild, but Popaj has no money, no property, no roof with which to shelter his family.

"All the things that I had were taken," he said. "My tractor. My car was ruined. I can't rebuild the house; I'll have to raze it. I had two cattle; they killed both of them."

Monday, he gave his testimony to interviewers from the war crimes tribunal. Because he was wearing only pajamas that night, because the Serbs were sloppy about the executions, Popaj survived and now can bear witness against a regime that is under international indictment.

It gives him little satisfaction.

"I didn't know for a week afterwards whether I was alive or dreaming," he said. "I can't sleep because of the terrible things I've seen."