CCTV footage which gave the lie to Louis De Zoysa’s claims of suffering an autistic meltdown suggests he retrieved a loaded revolver from a hidden holster up to 16 minutes before opening fire.

Sickening footage of Sergeant Matt Ratana being hit in the chest was played four times during the Crown’s closing speech alone – first at normal speed and then at progressively slower speeds, ending with a version an eighth as fast as real time.

As well as showing that De Zoysa, who was handcuffed to the rear, gave no warning, the film from an in-cell camera captured the exact actions of De Zoysa as he let off three rounds within three seconds.

Further footage from the scene of De Zoysa’s arrest and the 18 minutes he spent inside a police van shows how close officers came to discovering the antique revolver, which was loaded with six bullets.

It also caught the moments inside a police van when De Zoysa – with an officer sitting nearby – is believed to have removed the gun from a holster concealed under his clothing on his left side.

A rear-facing camera mounted on the van filmed a reversed image of the 25-year-old’s empty left hand as he exited the vehicle – with the gun in his non-dominant right hand already hidden under the rear vent of his overcoat.

De Zoysa’s temperature was then taken as part of Covid checks and he was taken into a holding cell for a follow-up search, where he sat on a bench with his back to the wall.

After being asked to stand, De Zoysa stood up and levelled the revolver at Sgt Ratana.

The first and fatal round struck Sgt Ratana in the chest, instantly throwing him backwards, while the second struck him in the leg as he was on the ground.

A third round hit the holding cell wall as another officer bravely fought to wrestle the weapon from De Zoysa, who caused himself brain damage with a fourth bullet.

In his closing speech to the jury at Northampton Crown Court, prosecution KC Duncan Penny said the footage showed deliberate and purposeful aiming of the weapon by De Zoysa, who had twisted his body in one movement to open fire.

Arguing that defence medical evidence suggesting that De Zoysa had experienced an autistic meltdown had been “tentative” and “conditional”, Mr Penny said of the CCTV footage: “Louis De Zoysa had purchased that weapon and he had manufactured ammunition to allow the antique firearm to work as a deadly weapon.

“He was asked direct questions which meant he could have told them (police) about the bullets and the gun. He did not do so.

“In the police van Louis De Zoysa took steps to arm himself with the gun – he held the gun in his hand and then under the vent of his coat.

“On the way into the police station Louis De Zoysa was still holding the gun and still hiding it under the vent of his coat.

“You might think the only purpose of that holster was to allow easy access to a weapon being carried in a concealed manner.

“Whilst he was in the van and during the journey he made the decision to seek to try and take hold of the lethal weapon.

“We suggest, in all likelihood, he had hold of the gun within a few minutes of being placed in the van.”

It is believed the gun was hidden on the left side of De Zoysa’s body, Mr Penny said, adding: “As a matter of straightforward physics, that means that the only hand that was in a position to get hold of the gun was his right hand.”

CCTV from inside the police van showed De Zoysa flicking his coat up, moving his right shoulder and grimacing, as handcuffs apparently cut into his wrists.

Mr Penny said of the footage: “If it’s the moment when he managed to take hold of the gun it is over sixteen minutes before Sergeant Ratana is shot.”

Commenting on the film of De Zoysa exiting the van, Mr Penny continued: “The right hand has been shoved up under the coat. Why take hold of the gun if you have no intention of using it?

“The gunman followed the target. In the context of this case, if that is right … the defence of diminished responsibility does not arise. The prosecution suggest his actions were purposeful.

“He knew what he was doing. He did not recoil in horror after the first shot and drop his gun. These, we suggest, were not uncontrolled actions – he was firing his gun at a selected target.”

Mr Penny said the CCTV clearly showed De Zoysa aiming two shots at Sgt Ratana, rather than the “random responses” that would be associated with the scenario claimed by the defence.

“All of these were conscious, deliberate decisions – they are shown on the CCTV,” Mr Penny said. “An autistic meltdown was not the cause. The prosecution therefore submit that Louis De Zoysa is guilty of murdering Sergeant Ratana.”