The men convicted of the notorious "Essex Boys" gangland murders have been told to "accept their fate" by a former police officer who worked on the case.
Jack Whomes and Michael Steele were jailed for life in 1998 for the execution of three men on isolated farmland at Rettendon in 1995.
The Criminal Case Review Commission (CCRC) is looking at fresh evidence the pair claim supports their innocence.
However, retired officer David Bright said the guilty verdict was "right".
Patrick Tate, Anthony Tucker and Craig Rolfe were gunned down with a pump-action shotgun after their Range Rover was ambushed in a row about drugs on 6 December 1995.
Steele, of Great Bentley, Essex, and Whomes, of Brockford, Suffolk, were found guilty of the killings in 1998 following a trial at the Old Bailey, but have always protested their innocence.
It is the fourth time the CCRC has reviewed the case, which inspired the 2000 film Essex Boys starring Sean Bean.
The first of those reviews was referred for appeal against their conviction, which was lost in 2006.
'Good barristers defending'
Former commander of Essex Police's crime operations division Mr Bright said: "When are they going to stop and accept their fate?"
"The evidence put before the jury was very, very good evidence. The trial ran a little over five months, it was well controlled by the judge, there were excellent barristers for the prosecution and equally very, very good barristers defending the two defendants.
"The jury listened intently throughout that time and came back, in my opinion, with the right one."
Earlier this year Whomes' minimum sentence was cut from 25 to just over 22 years, allowing him to apply for parole as early as 2020, because of his "exceptional progress" in prison.
The Essex Boys on film
- Essex Boys (2000)
- Rise of the Foot Soldier (2007) and Rise of the Foot Soldier II (2015)
- Bonded by Blood (2010) and Bonded by Blood 2 (2015)
- The Fall of the Essex Boys (2013)
- Essex Boys: Retribution (2013)
- Essex Boys: Law of Survival (2015)
- The Hit (2015)