Mr Nikitin's alleged crime is publicly to have exposed details of the radioactive contamination and lethal threat caused by Russia's rusting nuclear- powered Northern Fleet in the Arctic. But, instead of being hailed as an environmental hero, Russia's security services responded by accusing him of disclosing state secrets and slamming him behind bars.
He was arrested by the Federal Security Services (FSB) in February 1996 after contributing to a report on the fleet by the Norwegian environmental organisation, Bellona, which was subsequently seized by the Russians and banned.
He has spent 10 months of the past two and a half years in prison, the rest of the time confined to St Petersburg.
The case is highly sensitive to the Russians, as Mr Nikitin, 47, is a former nuclear safety inspector for the Soviet and Russia defence ministries.
He has complained of being harassed, followed and bugged, having his tyres slashed three times in once incident.
A judge has ruled that the trial, at St Petersburg City Court, will be partially open. It is being seen by human rights activists and others in the West - some of whom will have observers at the case - as a measure of whether the Russian authorities have weaned themselves off repressive Soviet habits.
The issue has been taken up with Moscow on different occasions by the United States, the European Union and the Council of Europe.
It is a "litmus test of the government's commitment to civil society and the rule of law", said Human Rights Watch in Moscow.
Amnesty International views Mr Nikitin as the first prisoner of conscience since Andrei Sakharov in 1980.
If convicted of the charges - which are enshrined in secret decrees - Mr Nikitin faces a maximum sentence of 20 years in prison. However, the court which is made up of a judge and two lay assessors, could return the case to the FSB for more investigation.
Founded in 1986, Bellona has long been a thorn in Moscow's side because of its investigations into nuclear waste dumping on the Kola peninsula in the Arctic, close to Norway's border. In 1995, it released pictures of dozens of spent nuclear fuel rods from a Russian submarine, each allegedly highly radioactive. They were lying on the open landscape.
While investigating the Nikitin case, the FSB raided Bellona's offices in Murmansk, confiscating computers, data disks and other material.
The security agency has since circulated claims that Mr Nikitin continued to use his military identification card to gain access to top-secret documents on Bellona's behalf after he retired from active service. Bellona maintains it used only voluntary and authorised sources in its report.Reuse content