Mandatory life sentences for murder in England and Wales are both unjust and outdated, legal experts said today.
The Homicide Review Advisory Group, which includes judges, academics and former QCs, said neither mandatory sentences nor the system for setting minimum terms allow for sentences to match individual crimes.
A so-called mercy killing attracts the same mandatory life penalty as serial killings, the group said.
It called for sentencing for murder to be discretionary.
The group's report added that the indefinite and misleading nature of life sentences - which may or may not involve a life spent behind bars - was both unjust and incomprehensible.
It added that the time has come for a move to fixed sentences for murder so that the exact circumstances of offences can be properly reflected by the courts.
The mandatory life sentence replaced the death penalty in 1965.
The group said it was brought in as a compromise to ensure the abolition of the death penalty made its way through both Houses of Parliament.
The starting point for a minimum term to be served for less serious murders is 15 years.
Having served their term, offenders are released on life licence, but can be recalled to prison at any time if they go on to breach its terms.
The report comes after research published last October showed there was no evidence of widespread support for mandatory life sentences for murder.
Fewer than one person in five believed that sentencing cases of murder was "about right", the study found.
Report authors law professors Barry Mitchell and Julian Roberts said serious consideration should be given to using mandatory life sentences for "particularly serious cases" only.
Prof Mitchell, from Coventry University, and Oxford University's Prof Roberts said they wanted to test the assumption that anything less than automatic indefinite jail terms would undermine public confidence in the criminal justice system.
Their study, funded by charity the Nuffield Foundation, found that the public had limited understanding of how convicted murderers were sentenced.
In particular, the vast majority of people wrongly assumed the murder rate in England and Wales has increased over the past decade, when it had actually begun to decline.
And a big proportion of those surveyed underestimated the length of time that most murderers spend in prison before being released on life licence.
More than 1,000 people were questioned across England and Wales.
In October this year, Justice Secretary Kenneth Clarke unveiled plans to extend the use of US-style mandatory life sentences to crimes other than murder for the first time.
The surprise announcement came just a day after he told MPs that mandatory sentences were not the British way and led to a game in which judges would look for any excuse not to hand down the set terms.
Magistrates and solicitors warned the "two strikes" approach would erode judges' discretion.
The move, part of plans to scrap the controversial indeterminate sentences for serious offences, would release hundreds of dangerous criminals on to the streets early, helping to slow the rising prison population by 2,500 places by 2030, a Ministry of Justice (MoJ) impact assessment showed.
Mr Clarke said that around 20 people a year could expect to receive the new mandatory sentence aimed at those guilty of two sexual or violent offences each deserving 10 years or more in jail.
Judges would retain the discretion not to impose a mandatory sentence if it would be unjust to do so, he added at the time, saying: "I find it difficult to imagine that anybody convicted of two such serious sexual and violent attacks wouldn't have been given life anyway."
A Ministry of Justice spokesman said: "We have no plans to abolish the mandatory life sentence for murder.
"The most serious crimes deserve the most serious sentences."