Lee Rigby’s killers could face whole-life jail terms if appeal court judges back use of the sentences in a key ruling next year.
Five judges are due to consider a number of cases involving the terms on January 24.
Mr Justice Sweeney said that he will wait to sentence Michael Adebolajo, 29, and Michael Adebowale, 22, until after that decision.
Recent cases that have provoked debate include Mark Bridger, who is appealing against his whole-life term for the murder of five-year-old April Jones.
Convicted murderer Jeremy Bamber has also waged a long legal battle against his sentence, along with serial killer Peter Moore and double killer Douglas Vinter.
However, earlier this year, the Attorney-General referred the sentence of triple killer Ian McLoughlin, 55, to the Court of Appeal for being too lenient.
Mr Justice Sweeney gave McLoughlin a life sentence with a minimum term of 40 years for the murder of a ‘’Good Samaritan’’ pensioner.
McLoughlin admitted killing Graham Buck in Little Gaddesden, Hertfordshire, in July, while on day release from HMP Spring Hill.
Mr Buck, 66, suffered fatal stab wounds when he responded to cries from the home of 86-year-old Francis Cory-Wright, a convicted paedophile, who was being robbed in the village near Berkhamsted.
McLoughlin was serving a life term for the murder of Brighton barman Peter Halls, whom he stabbed multiple times in 1992.
He had previously been jailed for the manslaughter of Len Delgatty, 49, in 1984, whom he hit over the head with a hammer after a row, before leaving his body in a cupboard.
Passing sentence at the Old Bailey, Mr Justice Sweeney said: “The implementation of a whole-life order within the current legislative framework in this country is in breach at the time of passing of sentence of article three of he European Convention.
“It is not appropriate to impose a whole-life term. However, even for a man of 55 years of age, the minimum term of years must be a very long one indeed.’’
However, after the sentence, Justice Secretary Chris Grayling said: “It is the Government’s clear view that whole-life tariffs should be available for the most serious offenders.
“That is the position clearly stated in our law, and what the public expects.
“The domestic law on this has not changed. We are considering the Government’s response to the ECtHR’s (European Court of Human Rights) recent ruling, but this in no way alters that fact and courts should continue to impose whole-life tariffs where they wish to do so.”