JERUSALEM -- He still does not know the crime that sent him to a prison camp in the desert, said Jad Isaac.
He is Palestinian, and that is offense enough, he said.
Dr. Isaac is a professor of biochemistry at Bethlehem University and was placed under "administrative detention" by Israeli authorities in 1988.
His case is strikingly similar to that of Sari Nusseibeh, another professor and moderate supporter of the Palestine Liberation Organization, who was arrested by Israeli authorities last week, accused of spying for Iraq during the Persian Gulf war. Mr. Nusseibeh was ordered held under administrative detention.
Mr. Nusseibeh's arrest has again drawn attention to the detention procedure that has been used by Israeli authorities to imprison 14,000 Palestinians or their supporters in the past three years, according to the military's own count.
An arrest under administrative detention requires little more than the signature of a military officer. There are no charges. There is no trial. The person detained may appear with a lawyer before TC judge,but the lawyer cannot see what is in the secret file used against his client.
On Sunday, after studying Mr. Nusseibeh's file, a Jerusalem judge reduced his six-month detention to three months "on an assumption that the war and related events would end within this period . . . the preventive aim of the detention would be met."
Israeli authorities defend the practice, first used here by the British when they controlled this land under a mandate more than four decades ago, as a necessity to remove instigators of trouble while protecting their own spies.
"Administrative detention is used in cases when, because of the sensitivity of the evidence or sources, you cannot divulge them in a court of law," said Col. Ranaan Gissin, a spokesman for the Israeli Defense Forces.
"When a person is engaged in an activity that could be harmful, we use administrative detention so they will cease immediately the activity," he said.
Palestinians say the arrests are a political tool. Many of those arrested are politically active, they say. The main detention camp is said to contain an unusually high proportion of educated Palestinians.
"It's practically a farce. We condemn the practice as a whole," said Yuval Ginbar, an official of B'tselem, a human rights organization. "People who are arrested are often those on the more theoretical side of the intifada," or Palestinian uprising.
An official of Amnesty International condemned the practice at a meeting of the United Nations Human Rights Commission in Geneva last week. Detention without trial is part of a "pattern of serious and widespread human rights violations in the Israeli-occupied territories," said Ingrid Kercher.
The arrest of Mr. Nusseibeh drew complaints from abroad as well as from liberal Israelis. All said he should be tried in public or released.
Some Palestinians note ironically the international flap over the arrest of Mr. Nusseibeh, who was educated at Oxford and Harvard, when thousands of lesser-known Palestinians are routinely detained with no outcry.
"It is nothing new," said Mahmoud Salamet of the Palestinian Human Rights Information Center. Because the six-month detention term is renewable, "we know of people who have been in for more than two years" with no charges against them, he said.
Dr. Isaac was confined for five months. It was a fairly short term, but not an easy one.
He was arrested and led away blindfolded in front of his wife and children during a sweep by Israeli authorities through a town on the West Bank that had staged a tax protest, he said.
He was taken to Ketsiot, a prison camp in the Negev desert in southern Israel. Most administrative detainees are held there. According to the Israeli military, there are about 1,440 men currently under administrative detention.
Described by friends as a bookish, unassuming academic, the 43-year-old professor was introduced at Ketsiot to a violent rule.
"Solitary confinement and beating were the norm," he said. "Tear gas was used for every reason. Three times while I was there, they surrounded the compound, ordered everyone into a tent and sprayed tear gas inside. It was used as punishment."
Dr. Isaac described his experiences, for what he said was the first time, to a reporter because he was angered by the arrest of Mr. Nusseibeh. He spoke by telephone from his home in the West Bank, which has been under curfew and off-limits for travel since Jan. 17. His description of his confinement was confirmed by others familiar with the prison.
Ketsiot is a huge patchwork of tents in the sandy desert, divided into compounds by high fences sheathed in plastic and barbed wire. Dr. Isaac was put in a tent with 27 other men.
There was one latrine and two showers for about 200 men. Because of water restrictions, showers were infrequent. The three meals a day were mostly beans, he said, with fish once a week and sometimes some processed meat.
Vegetables and fruits "were unheard of," he said, and professional dietitians among the detainees calculated the nutritional content was just barely enough for survival.
They slept on wooden slats with a thin rubber mat and six blankets in the winter. That wasn't enough.
"The cold of the desert in the winter is something I will never forget," he said. With little humidity, the freezing air is sharp and hard, he said. There was no heat.
"I was always cold. I felt as if somebody had a nail and worked it inside my bones and then moved it around."
In the summer, the sun baked the camp at temperatures of more than 100 degrees.
Technically, detainees are allowed visits from family members. But because Ketsiot is in a closed military area, none could come.
After his release, he returned to teaching. But his movement is restricted. He cannot cross the invisible boundary into Israel or Jerusalem without special permission.
Dr. Isaac insists he is not bitter.
"To score political points is not the point of the game," he said. "I am ready to forgive. But I don't think I can forget."