A man who allegedly murdered a Metropolitan Police custody sergeant has said he felt “sad” that the officer died.

Louis De Zoysa, 25, is accused of shooting dead Sergeant Matt Ratana, from Goring, at a custody block in Croydon, south London, on September 25 2020 while he was handcuffed.

The prosecution alleges De Zoysa, who denies murder, “pulled the trigger on purpose four times” while he was handcuffed in a holding room at the custody centre, the first and second shots hitting 54-year-old Sgt Ratana, the third hitting the wall during a struggle with officers, and a fourth hitting De Zoysa himself.

Giving evidence in a modified way at Northampton Crown Court, because of communication difficulties caused by brain damage due to a gunshot wound, De Zoysa nodded when asked if he knew that Sgt Ratana had died and said he felt “sad” about it.

De Zoysa agreed that the CCTV footage showed him firing a gun at the sergeant and that the prosecution say he murdered him.

Asked what murder meant, De Zoysa said: “Kill.”

Imran Khan KC, defending, asked: “Are you guilty of murder, Louis?”

De Zoysa told his barrister “no” but later said he did not know what “guilty” meant.

He went on to deny wanting or meaning to kill Sgt Ratana or cause him “really serious harm” – which he said meant “scar”.

De Zoysa sat in a wheelchair in the well of the court with a small whiteboard and marker on the desk in front of him.

He promised to tell the truth in a modified oath and has given evidence using a combination of speech, writing and drawing.

De Zoysa said he had autism and would regularly get stressed, leading him to punch chairs and walls.

Questioned on his family, De Zoysa confirmed his father used to “beat” him over “trivial matters”.

He wrote the word “coke” on his whiteboard before adding: “He is a criminal. He used to be a drug dealer.”

The defendant drew a stickman wearing a cast on one leg before confirming that his father hit and broke his leg.

The incident caused him to feel a “brewing” inside of him which he could not further explain, the court heard.

De Zoysa went on to say he hit his father on the head using a metal rod in an apparent separate incident and did it out of “panic” – a feeling which he said was “possibly” caused by his autism.

He was arrested for “fighting” his father in June 2019.

Jurors watched police body-worn video of De Zoysa’s 2019 arrest in which an officer could be heard saying: “He’s kicked his father off his bike.”

Asked about the incident, De Zoysa said his dad was upsetting him and talking “too loud”.

The jury heard more about the defendant’s home life including an inference that he liked eating dinner alone because there was “violence” at the dinner table with his “family” which was “crazy”.

He confirmed that he broke the stairs in his family home and set a carpet on fire because he was “upset”.

The court also heard he smoked cannabis because of “stress” which helped him feel “mellow”.

Jurors were told De Zoysa was bullied at school, the defendant explaining that his peers threw chains at him because he was “vulnerable” and an “easy target”.

But he received three As at A-Level for Chemistry, Physics and Maths and attended University College London – although he did not finish his degree.

He worked in coding at HMRC and told the jury he got on well with his colleagues.

The defendant had been arrested on London Road, Norbury, south London, during the early hours of September 25 2020, after a stop and search by officers found he had cannabis and seven rounds of ammunition.

Officers did not know De Zoysa, of Banstead, Surrey, had a gun until it was used to shoot Sgt Ratana.

Jurors have been told they will have to consider whether De Zoysa deliberately fired the revolver and the question of diminished responsibility.

Mr Khan previously told the jury that the defendant was suffering an autistic meltdown at the time of the shooting.

The trial continues.