A bid to obtain a death certificate for Lord Lucan reaches the High Court today.
The legal move by the peer's only son, George Bingham, is at an early stage and senior official Master Teverson is expected to deal with preliminary issues about how it should proceed.
Lord Lucan vanished after Sandra Rivett, nanny to his three children, was found murdered at the family home at 46 Lower Belgrave Street, central London, on November 7 1974.
Even though he was officially declared dead by the High Court in 1999, there have been reported sightings in Australia, Ireland, South Africa and New Zealand, and even claims that he fled to India and lived life as a hippy called "Jungly Barry".
Lord Bingham has applied under the Presumption of Death Act, which came into effect a year ago, so he can inherit the title as 8th Earl.
The legislation was the result of a campaign supported by relatives of high-profile missing people including chef Claudia Lawrence, who disappeared in York in 2009, and Manic Street Preachers guitarist Richey Edwards, who went missing in 1995.
Lord Bingham says the 1999 declaration had not proved death "for all purposes" and the new law allows for a "more complete process".
But his application in London faces an objection from Miss Rivett's son, Neil Berriman.
Mr Berriman, 47, has told the Daily Mail: "I don't know if Lord Lucan is alive or not - but I want justice. There have been too many cover-ups already and he should not be declared dead. If Lord Lucan is still alive, he should be prosecuted."
The application for a death certificate was "very, very insensitive" and one should only be issued when the "truth comes out" about his mother's death, he added.
On the night of Lord Lucan's disappearance the nanny's attacker also turned on Lord Bingham's mother, Lady Lucan, beating her severely before she managed to escape and raise the alarm at a nearby pub.
Lord Lucan's car was found abandoned and soaked in blood in Newhaven, East Sussex, and an inquest jury declared the wealthy peer the killer a year later.