Jeremy Bamber and two other murderers will have their appeal that keeping them behind bars for the rest of their lives is a breach of their human rights heard by the Grand Chamber of the European Court of Human Rights.
Bamber received a life sentence for shooting dead five members of his family in Essex in 1986.
He has always protested his innocence and claims his schizophrenic sister Sheila Caffell shot her parents and her six-year-old twin sons before turning the gun on herself.
Bamber has previously attempted to get his conviction overturned but it has been upheld several times.
More top news
Protesters force cancellation of controversial 'human zoo' show which has been dubbed racist and offensive.
The Silverton family are celebrating the birth of the first baby girl in a century, breaking a streak of 21 boys over four generations.
The 100 leaders did not agree on concrete proposals, but the meeting has raised hopes for concrete international agreement next December.