By Tabitha Morgan BBC correspondent, Athens

Giotopoulos (l) was November 17's leader and Koufodinas its main hitman

In a heavily guarded court in Athens, a judge found leading members of the November 17 group guilty of multiple charges of murder.

The trial has lasted for 10 months and received testimony from 500 witnesses.

Since 1975 the group had carried out a series of murders, bombings and armed robberies in Greece, without a single member being caught.

Conspiracy theories

The ruling by Judge Mihalis Margaritis on Alexandros Giotopoulos, Dimitris Koufodinas and Savvas Xiros will come as an enormous relief.

Greek police, attempting to track down members of the group, had appeared hopelessly out of their depth.

According to the son of one of the group's victims, the police were guilty of "devastating incompetence."

Without any clues as to exactly who N17 were, conspiracy theories flourished.

Most popular was that which claimed the group had links with senior government figures and was therefore being protected.

The fact is that in its early years the group did enjoy a certain amount of popular support among ordinary Greeks, who, while they might have condemned N17's methods, definitely endorsed it's ideological aims.

We know that some members of N17 are still at large, I just hope they will continue to stay silent Prosecution lawyer Alexandros Lycourezos

November 17 took its name from the date of a left-wing student uprising in 1973 against the military junta which ruled Greece from 1967-1974.

It is a date which continues to have considerable emotional resonance for Greeks, and by adopting it as their name the group sought to link itself implicitly with an heroic episode in the country's past.

After the fall of the colonels in 1974 many Greeks felt that the government of Konstantinos Karamanlis which succeeded them did too little to punish those who had been involved in the US-backed regime.

As a result there was relatively little public outrage after the killings of N17's early victims, who included Athens CIA chief, Richard Welch, and former police torturer, Evangelos Mallios.

Over the next 25 years the group went on to kill 15 more Greeks, another three Americans, and a Turkish diplomat.

Changed view

But whatever public sympathy the group still retained appeared to evaporate after the killing of Brigadier Stephen Saunders, gunned down in June 2000 while sitting in his car in an Athens traffic jam.

People started to see the craziness of terrorism for the first time Yiorgios Momferatos, father killed by the group in 1985.

N17 claimed to have targeted the British military attache as an expression of their opposition to Nato's bombing of Serbia.

Immediately after the murder, his widow Heather, made an emotional televised appeal for his killers to be found.

For many Greeks this was the first time they had been brought face to face with the human cost of the group's actions.

"People started to see the craziness of terrorism for the first time," said Yiorgios Momferatos, whose father was killed by the group in 1985.

"Until then a substantial part of the population just felt N17 was getting rid of 'bad' people".

Speculation continues

But despite growing public revulsion at their actions, N17 continues to have a certain mystique in the public imagination.

There has been much speculation since the 19 defendants were arrested about who was responsible for the group's early assassinations.

With the notable exception of Giotopoulos, most of those found guilty of N17's crimes would have only been in their early teens when the killings started.

"We know that some members of N17 are still at large," said prosecution lawyer Alexandros Lycourezos. "I just hope they will continue to stay silent."

With the Olympic Games taking place in Athens next summer, the government will be hoping that the conviction of the 15 group members will mark the end of a gruesome chapter in the country's history.