Louis De Zoysa shot Sgt Matt Ratana in a holding cell after hiding a revolver from police officers for about 50 minutes.
A cannabis user who shot dead a custody sergeant while handcuffed in a police cell has been handed a whole-life sentence.
Gun fanatic Louis De Zoysa was convicted of murder last month, after jurors were shown distressing CCTV footage of the 26-year-old using a legally-bought revolver to gun down Sgt Matt Ratana.
Sgt Ratana died in hospital despite the efforts of medical staff, after being struck by two bullets in a holding cell in Croydon, south London, in September 2020.
The jury which convicted De Zoysa, a former tax office data analyst, was not told that a shortened infantry rifle, numerous types of ammunition, a pipe gun and a dummy launcher were found at his rented property after the killing.
Sentencing De Zoysa at Northampton Crown Court on Thursday, High Court judge Mr Justice Jeremy Johnson told him: “You acted in cold blood. You intended to kill Sergeant Ratana.
“You aimed the gun at his chest at near point-blank range. Even as he fell you re-aimed and fired a second shot at him.
“The aggravating factors outweigh the mitigating factors. There is therefore no justification to depart from the starting point of a whole-life order.”
De Zoysa, who is expected to be held at HMP Belmarsh in south-east London, showed no obvious reaction as he was told he will spend the rest of his life in prison.
De Zoysa, of Banstead, Surrey, claimed diminished responsibility but was found guilty after a jury decided he pulled the antique weapon’s trigger deliberately to fire homemade bullets, and had not suffered an autistic meltdown.