Andrus Giedraitis, aged 31, of Riseholme Road, and Martynas Kupstys, were put behind bars for the murder of Ivans Zdanovics, 24.
The victim was found dead in a smoke-damaged house in Etherington Street on January 17 2014.
His death was caused by smoke inhalation and there were five separate seats of fire - each deliberately ignited - Mr Justice Globe told London’s Appeal Court today.
A fingerprint of Kupstys, 26, of Aegir Close, was found in soot on a wall and his DNA was discovered on a black holdall.
The prosecution case was that the two men had ‘jointly murdered’ Mr Zdanovics, with Kupstys lighting the fire with encouragement from Giedraitis.
Kupstys admitted starting the fire but denied intending to kill the victim or cause him serious harm, while Giedraitis denied being at the house when the fires started.
But both men were convicted of murder and caged at Lincoln Crown Court on April 14 last year.
Giedraitis got a minimum 21 years behind bars and Kupstys was ordered to serve at least 25 years.
Andrew Jefferies QC, for Giedraitis, challenged his conviction today, arguing it was “unsafe”.
He said his “continued and admitted presence” with self-confessed fire starter - Kupstys - was “insufficient to infer encouragement”.
Kupstys had denied he was egged on by Giedraitis, admitted ‘acting alone’ and said his co-defendant was not in the house at the time the fires were lit.
There was ‘scant if any evidence’ to suggest Giedraitis encouraged Kupstys by his ‘mere presence’, said Mr Jefferies.
CCTV footage only showed him in the vicinity of the fire scene, not inside the home, added the barrister.
“In our judgment, Giedraitis’ ground of appeal in relation to the issue of encouragement is an arguable ground of appeal,” said Mr Justice Globe.
The judge, who was sitting with Lord Justice Hamblen and Judge John Wait, granted Giedraitis permission to appeal against his murder conviction.
The full appeal hearing will take place at a later date, yet to be set.