Four police officers will begin a year's prison sentence in a month, after the Supreme Court on Sunday rejected their appeal to overturn the sentence.

The four, dubbed "the avengers," were convicted for attempting a series of bomb attacks against an alleged crime family in Nahariya. The four officers said they intended to ask the president for a pardon.

Policemen Rami Musa, Yaniv Ashur, Eldad Hadad and Yossi Levi were convicted last October of planting explosives under a car belonging to Michael Mor - the alleged head of an organized crime syndicate in northern Israel - and at the home of his nephew, Rafi Ben Shalom. The explosives placed at Ben Shalom's house went off, causing damage to the building, but those placed under Mor's vehicle failed to detonate due to a technical malfunction.

"The police officers used criminals' methods, not methods of law enforcement officials. They turned from defenders of the law to offenders," wrote the justices in their ruling.

The officers intended to strike Mor and his associates due to threats they allegedly made against the officers and their families, as well as against public figures in Nahariya. Mor was also suspected of throwing a grenade at one of the officers' homes.

The District Court gave them a year's prison sentence and a year's suspended sentence.

The officers appealed to the Supreme Court against both conviction and sentence, claiming they did not act in vengeance but to deter Mor from harming them and their families, and to prompt the police to act against the criminals.

The state initially also appealed to the Supreme Court demanding a harsher sentence for the defendants, but later retracted its appeal.

Justices Salim Joubran, Yoram Danziger and Isaac Amit emphasized in their ruling this week that the four had undermined the public's confidence in the law enforcement authorities and failed miserably in the test of protecting the rule of law. They ruled that in this light, a severe penalty was needed for their actions.

"We must protect Israel's officers and show zero tolerance for anything that harms them, to provide them with the effective tools for fighting crime and violence," wrote the justices.

But the court rejected the defendants' claim of acting in self-defense, saying their arguments distorted the meaning of self-defense and endangered the foundations of democratic society. "When officers act outside the law, they directly harm the way the police functions and the public's trust in it," the justices wrote.

One of the justices favored handing down a three-year jail sentence on the officers, as well as a one-year suspended sentence, but the other two justices on the panel upheld the one-year sentence handed down by the District Court.

"The police will look into the sentence's implications before responding to the judgment," a police spokesperson said.

In their testimony, the policemen told the court they had acted the way they did because "the system was powerless to defend them."

One of the convicted officers, Yossi Levy, said there is wide public support and strong police support for the four. "A number of policemen's organizations and dozens of local authority heads have signed their support for a pardon. I hope we'll manage to avoid going to prison," he told Haaretz.

"We're deeply disappointed," Levy said on leaving the courtroom. "We've paid three long, hard years. That should have been enough. We got the message."

Levy said the officers will ask the police and police commissioner to support their families while they serve their sentences.