Every morning this week, the gleaming halls of Spain's Supreme Court were thronged with the sort of people who like to wear very dark glasses indoors. The white marble columns were dazzling in the brilliant sunlight, which had brought a belated summer to Madrid, but the fashion for shades at the Dirty War trial had little to do with eye strain. One of the defendants went further, and, like Martin Cahill, entered the building in a motorcycle helmet to cheat the battery of cameras outside.

This man was not a normal criminal, however. Like most of his co-defendants, Michel Dominguez is a former cop. A bizarre assortment of anti-terrorist commanders, spooks, self-confessed state terrorists, convicted frauds, top politicians and ETA sympathisers congregated in the court's spacious corridors at every session.

As they huddled or strolled, they were shadowed by bodyguards, attended by lawyers, and discreetly pursued by journalists.

Many of the principal players in this drama are not used to coming out in daylight hours at all. These are people who like to ask the questions, in darkened rooms with the light focused on the suspect.

Now they are being asked for answers, in the full glare of national and international publicity. The court's questions put an unprecedented focus on what the former prime minister, Felipe Gonzalez, a future witness at the trial, once colourfully called "the sewers of the State".

It's no wonder the defendants and their associates spend a fortune on Ray-Bans. The politicians, of course, are used to the exposure, but few of them would have chosen this particular forum.

A former Interior Minister, Jose Barrionuevo, and his deputy, Rafael Vera, face charges of kidnapping, membership of an armed gang, and misuse of public funds. They are looking at 23 years in jail.

Nine of their subordinates, including the elite of the 1980s anti-terrorist high command, have pleaded guilty. Several of them allege they were acting under the personal instructions of Barrionuevo. So does Ricardo Damborenea, who revelled in the nicknames "Dambo" or "the sheriff of the Basque Country" for his gung-ho, anti-terrorist rhetoric in the 1980s.

Damborenea was the Socialist Party boss in Bilbao when ETA's terrorist campaign in pursuit of an independent Basque country was at its most ferocious. It was an open secret that he believed the democratic state should fight that terrorism "with its own weapons".

Last Tuesday, in the best traditions of ham courtroom drama, Barrionuevo lost his self-control and angrily denounced Damborenea for playing "an informer's role" in unveiling the state's involvement in setting up anti-ETA death squads. That unfortunate - or revealing - phrase is likely to haunt the former minister.

In October, 1983, according to Damborenea's account, he advised the security chief in Bilbao on the kidnapping of Segundo Marey, a French resident mistaken for an ETA leader. This kidnapping, which is the subject of the current trial, was the first act ion acknowledged by the Grupos Anti- terroristas de Liberacion, otherwise known as GAL.

This organisation went on to kill 27 people, nine of them innocent of any terrorist links. The GAL campaign was partly aimed at pressurising the French authorities to extradite ETA leaders, who had enjoyed a kind of sanctuary north of the Pyrenees. Barrionuevo conceded in court that French collaboration had, indeed, improved remarkably by the time of the last major GAL attack, in 1986.

Damborenea is a tall, angular figure with a wry, crumpled face. He strides firmly up and down the corridors, chain-smoking, more often alone than the other defendants. In the course of a 10-minute recess, he passes within inches of Barrionuevo's and Vera's entourage several times.

Around the next corner he will find Kepa Landa, a prosecution lawyer with a neat, meticulous manner and intense but distant eyes. Landa is also a leading member of Herri Batasuna, ETA's political wing.

Avoiding eye contact without colliding with the enemy is a useful skill during around any court case. In these shining hallways it is honed to a high art. Damborenea told the court he decided to reveal his own role in GAL because he was not prepared to see more anti-terrorist commanders going to jail for actions which had been authorised by his party and government.

He claims that not only Barrionuevo, but also Felipe Gonzalez, approved the GAL strategy. In 1995, he handed over voluntarily a document, which he claims was an agreed military intelligence blueprint for dirty war operations, to the investigating magistrate.

This 1983 document argues that "kidnapping and disappearances" are "preferable" to the straightforward "elimination" of terrorists. Assassinations may actually strengthen the resolve of the enemy, the analysis says, but disappearances create anxiety and can produce information.

Several months later, the GAL campaign opened with at least three kidnappings. The other two victims were not as "lucky" as Marey. Their bones, bearing signs of torture, were found buried in quicklime in Alicante in 1985, though they would not be identified for another 10 years.

Damborenea's production of this document led to the most extravagant of many outlandish episodes in the investigation of the GAL, which now has repercussions far beyond the domain of the Basque conflict.

This week, the European newspaper published an article which argued that, if Barrionuevo is convicted, Gonzalez might be as big an embarrassment as a future EU Commission President as Kurt Waldheim was at the UN.

A military intelligence operations chief, Col Alberto Perote, turned out to have illegally removed hundreds of classified documents from his office. A number of these, including Damborenea's document, which appear to implicate the army, and possibly Gonzalez himself, in GAL, were systematically leaked.

They were published by El Mundo, a newspaper deeply hostile to the Socialist government. Perote seems to have been financed by Mario Conde, a disgraced banker who blames Gonzalez for his troubles. This saga gives some substance to Barrionuevo's claim that the case against him has been politically manipulated, though such manipulation hardly invalidates the evidence.

In a final grotesque twist, a video showing the El Mundo's editor, Pedro J. Ramirez, engaged in transvestite and other sex games with his mistress, suddenly turned up all over Spain last November. Socialist leaders, including Gonzalez, could hardly contain their glee. The video has been linked, in a separate court case, to associates of Rafael Vera.

The dirty war keeps churning up new kinds of filth, 12 years after it ended. Perote, now serving a jail sentence for withdrawing the documents, came to the Supreme Court on Tuesday.

ON the witness stand, he attempted to walk a tightrope between denying any direct involvement by military intelligence in the GAL, and asserting that they were well aware of its activities. This information, he insists, was transmitted directly to Gonalez. The colonel's former commanding officer, a general, rejected this allegation on Wednesday. Perote, who wore no sunglasses and has the baleful eyes of a man who has seen everything, watched him from the press box, utterly impassive.

Barrionuevo has attempted to argue the Socialists are not only innocent as charged, but also actually pursued and dismantled the GAL in 1986. Asked if his unit had been ordered to investigate the GAL, Perote replied laconically: "On the contrary." Yet he often had as many as 40 agents operating on French territory, in the very towns where the GAL were most active.

As in most court cases, the general atmosphere is often lighter than you might expect, sometimes weirdly so. Some of the former sewer-dwellers have come to love the limelight with all the passion of Hollywood wannabes.

Jose Amedo was the first police officer to be convicted for GAL crimes, in 1991. In 1994, he helped initiate the present case by turning state's evidence. When I interviewed him last year, he told me he enjoyed his national profile "stupendously well". Going into court on Monday, he grabbed my arm and wished me "an enjoyable time in there".

It was hardly the right word, but there was certainly an element of theatrical entertainment involved in the hearings. That was as long as you could forget the TV images of Segundo Marey from 1983, too terrified to take off his own blindfold. He had just spent 10 days at the pleasure of Amedo, his bosses, and, if the court so proves, their bosses as well.

Marey will give evidence on Tuesday. By a strange coincidence, just around the corner from the Supreme Court, another kidnap hearing is taking place. The ETA members who held a prison officer in ghastly conditions for 500 days defiantly claim that they gave him better food than they get in jail.

The callousness of the terrorists is breathtaking. The Supreme Court is revealing, however, that ETA has not had a monopoly on callousness, or terrorism, over the last 15 years.