Moscow City Court judge Eduard Chuvashov was shot contract-style in the stairwell of his apartment building in central Moscow, Russia's top investigative body said.
The murderer used a silencer and left no shells, but investigators obtained footage from surveillance cameras showing a tall Slavic man, about 30-years-old, coming out of Chuvashov's apartment building shortly after the killing, it said.
"We have definitive leads," investigator Pyotr Titov said in televised remarks.
A leading rights group pointed the finger at a far-right ultranationalist group with alleged ties to Kremlin-backed youth movements, saying it may have links to the murder and incited hatred for Chuvashov on the Internet. A nationalist leader denied the accusations.
Chuvashov, 47, presided over several high-profile cases that involved hate killings committed by neo-Nazis and skinheads.
In February, Chuvashov presided over the trial of the White Wolves, a gang of mostly teenaged skinheads who kicked and stabbed their victims to death, often videotaping the attacks and posting them online. They were convicted by a jury of the killings of six Central Asian people and Chuvashov sentenced them to up to 23 years in jail.
Russia has experienced a surge of xenophobia and racially-motivated assaults in the years after the Soviet collapse, and the number of neo-Nazi groups has mushroomed.
As the nation struggles through an ongoing economic meltdown, nationalist groups have targeted dark-skinned migrants from ex-Soviet Central Asian nations and Russia's own North Caucasus region, accusing them of stealing jobs from ethnic Russians.
Chuvashov began receiving threats during the trial, a Moscow-based hate crime monitoring group, Sova, said.
The group's deputy director, Galina Kozhevnikova, said a leader of ultranationalist group Russky Obraz wrote in his blog in January that Chuvashov advocated the killing of ethnic Russians.
Alexander Baranovsky, who allegedly wrote the post, said that "nationalists are a very useful bogey man that can be accused of any big crime these days."
"Nationalists never had any complaints about Chuvashov; the way he judged the (White Wolves) trial was normal," Baranovsky said.
Russian anti-racist activists and rights groups also claimed that Russky Obraz had ties with Young Russia, one of several government-funded groups known for street rallies and harassment of Kremlin political opponents.
Young Russia and its leader, a member of the Russian parliament, has denied such links.
So far this year, 12 people have been killed and more than 70 wounded in racist attacks, the Sova center said. In 2009, a total of 71 people were killed and 333 wounded, it said.
Sova's Kozhevnikova said that Russian far-right nationalists are increasingly targeting officials and activists who oppose violent nationalism. "They are facing more and more danger these days," she told the AP.