BUENOS AIRES - Argentine public prosecutors have always needed steely nerves to investigate high ranking officials, business tycoons and criminals: threats to kidnap their children, blackmail and attempts to impeach them come with the turf.But even to the most hardened, the mysterious death last month of prosecutor Alberto Nisman the night before he was to testify about his allegations that President Cristina Fernandez tried to derail his probe into a bombing attack came as a shock.Some say it also laid bare a deep-seated culture of intimidation and meddling in Argentina's courts."Shots have been fired at my house. They have tried to kidnap my kids, filled my car with fish bait and threatened my parents," said senior prosecutor Carlos Rivolo of past investigations into senior officials."But until now there had not been a death."Rivolo is part of a group of prosecutors that has frequently locked horns with the government and has called for a silent march through Buenos Aires on February 18 to honor Nisman.Almost four weeks after Nisman's death, it is still unknown if the father-of-two shot himself in the head or was murdered.Nisman had accused Fernandez of trying to cover-up Iran's alleged involvement in the 1994 bombing of a Jewish community center in Buenos Aires that killed 85 people. He warned friends he might be killed for his work and his death sent shockwaves through Argentina.Conspiracy theories abound, with some pointing at Fernandez, though she blames rogue state security agents who she says duped Nisman into making his allegations as part of a campaign against her and then killed him when he was of no more use to them."Regardless of who did it, it is as scandalous a political death as we have had in 30 years, that's why everyone is so upset," said one prosecutor requesting anonymity.Organizers of next week's march say it will not be political, but it is fast becoming a platform for complaints over the intimidation of prosecutors and judges."The Nisman case is the first of its kind and may not be the last," said prosecutor Carlos Stornelli. He called for the government to guarantee that investigators could work "with security and independence even when they are probing it".The independence of Argentina's judiciary has long been in question.It turned a blind eye to the murder of thousands of suspected leftists during 1976-83 military dictatorship and in the three decades since democracy was restored, Argentines have grown weary of grand-scale corruption scandals.When prosecutors are appointed to investigate, they are often intimidated and cases shut down."There is clearly a lot of meddling in high profile political cases," said a diplomatic source.Rivolo said that during an investigation into one politically sensitive corruption case he received photographs of himself and his girlfriend with threats to expose his infidelity to his wife.His blackmailers were unaware he had already separated from his wife. He was later stripped of the case after being accused of bias.Polls show a strong majority of Argentines expect never to know the truth behind Nisman's demise.Fernandez's leftist government was swift to denounce Nisman's allegations against her as "absurd" and labeled aspects of the probe into his death an "embarrassing spectacle".Some prosecutors say privately that they hope October's presidential election will bring in a government more committed to an independent judiciary.Argentina's constitution does not allow presidents to hold office for three consecutive terms so Fernandez will not be running for re-election.Daniel Sabsay, law professor at the University of Buenos Aires, said Fernandez tightened her grip on the judiciary in 2012 when she named loyalist Alejandra Gils Carbo as chief prosecutor - a move approved by the Senate.Carbo "acts as if she were a branch of the executive power" and punishes those who investigate alleged corruption by officials in or close to the government, said Sabsay. "We are now living in this strange situation of a constant battle within the judicial sector."A spokesman for the prosecutor general declined to comment on Carbo's record in the job or her relationship with Fernandez and her government.In 2013, Carbo suspended prosecutor Jose Maria Campagnoli for misconduct in his probe into businessman Lazaro Baez, who is a friend of the president's family and was accused of embezzling and laundering $65 million."This was to discipline prosecutors, to say 'If you get in our way you will end up like Campagnoli'," said the prosecutor who spoke on condition of anonymity.Baez denies any wrongdoing.Prosecutors behind next Wednesday's march anticipate tens of thousands of people will demonstrate against intimidation.The opposition's front-running presidential candidates, Mauricio Macri and Sergio Massa, are expected to take part. They have both promised to fight impunity but have given scant details on how.The government says the silent march is part of a broader political attack waged by Fernandez' enemies."They can have their silence. Maybe it's just that they have nothing to say," Fernandez told supporters on Wednesday.Following Nisman's death, impunity and interference in the judiciary are almost certain to be hot topics in the run-up to the election."What is at stake is the republic," said legal expert and former prosecutor Pablo Lanusse. "They managed to hush Alberto Nisman but they cannot silence us all."