On Wednesday, Bingham used new legislation to successfully apply for a death certificate to be issued.
"My own personal view, and it was one I took I think as an 8-year-old boy, is he's unfortunately been dead since that time," Bingham, now Earl of Lucan, said outside court.
"In the circumstances I think it's quite possible he saw his life at an end, regardless of guilt or otherwise.
"Being dragged through the courts and through the media would have destroyed his personal life, his career and the chances of getting custody of his children back.
"That may well have pushed a man to end his own life but I have no idea."
One of numerous theories about what became of Lucan, who would now be 81, was that he shot himself and was then fed to tigers at the zoo of his friend John Aspinall.
Aspinall said in 2000 that Lucan had weighted himself down with a stone and drowned himself in the English Channel.
Rivett's son Neil Berriman told reporters he bore no ill feeling towards Bingham but hoped the mystery would be explained with the help of new evidence in the next year.
"There is no getting away from the fact that whatever happened that night, Lucan is guilty of something in my eyes," he said, without giving details of the evidence he referred to.
Some theories about what became of Lord Lucan
•November 7, 1974 - Seventh Earl of Lucan disappears after body of Sandra Rivett, nanny to his three children, is found at the family home in central London.
•Lady Lucan says at the time her husband admitted committing the crime and that it was a mistake. It is also reported she believes Lucan jumped to his death off a ferry leaving Newhaven, East Sussex.
•Lucan's car is found abandoned and soaked in blood in Newhaven and an inquest jury declares the wealthy peer the killer a year later.
•January 1975 - He is supposedly spotted in Melbourne and five months later he is apparently in Cherbourg and St Malo, France.
•He is apparently spotted in Cape Town, Mozambique and then Bulawayo. Police in Cape Town go so far as to check fingerprints on a beer glass, reputedly held by the peer.
•1978 - Scotland Yard asks Barbados police to investigate a report a British resident there is sending money to Lucan in South America.
•He is also reportedly sighted on an ex-Nazi colony in Paraguay, at a sheep station in the Australian outback, backpacking on Mount Etna and working as a waiter in San Francisco. One couple report seeing him in a private hospital in Johannesburg in 1995.
•There are even claims that he fled to India and lived life as a hippie called "Jungly Barry".
•1987 - Journalist Sally Moore publishes Lucan - Not Guilty, a book that claims an intruder murdered the nanny and attacked Lady Lucan.
•1999 - He is officially declared dead by the High Court but reported sightings of him continue to be made around the world.
•An ITV drama based on John Pearson's book The Gamblers claims Lucan's high-rolling friends, who included Sir James Goldsmith and John Aspinall, spirited him out of the country after the murder.
•2007 - The hunt for Lucan is focused on the small New Zealand township of Marton after claims that he may have been living in a car there.
•2012 - Lucan's brother Hugh Bingham says he is "sure" the missing peer fled to Africa following the nanny's murder. But he then says he is unsure if his sibling is alive or dead.
•In Dead Lucky, former senior Scotland Yard detective Duncan MacLaughlin says Lucan fled to Goa where he lived a hippie lifestyle as Barry Halpin until his death in 1996.
•Some say he was held to ransom by the IRA or shot himself and asked that his remains be fed to the tigers at the zoo in Kent, which belonged to Aspinall.
-AAP
