Thuvan Prawesh Sawal had no motive to murder his mate, Canterbury dairy farmer Sameera Chandrasena Battelage, his defence argued today.

Sawal denies the February 2012 killing, and instead blames murder co-accused Viraj Alahakoon.

Sawal claims he witnessed Alahakoon cut the throat of Mr Battelage as he slept at his Oxford farmhouse in a murderous, jealous rage after learning of an affair.

On the nineteenth day of the High Court trial in Christchurch, Sawal's defence counsel John Brandts-Giesen began summing up, saying: "Friends do not kill friends, unless there is a motive that far outweighs that friendship."

Alahakoon, 35, and Sawal, a 24-year-old overstayer, blame each other for the murder of Mr Battelage at his farmhouse on Domain Rd, just outside Oxford in North Canterbury on February 23 last year.

The Crown says the pair plotted to kill Mr Battelage after he had an affair with a woman Alahakoon knew.

Together, they stabbed or cut Mr Battelage's neck six times before dousing his body in petrol and setting it alight.

The court has heard that Mr Battelage was surprised when the pair showed up at his rented rural property on the evening of February 22, last year.

Alahakoon, who'd just been laid off as a jeweller, and Sawal, a Sri Lankan overstayer, say they wanted to confront him over the affair.

Today, Mr Brandts-Giesen said the happy go-lucky Sawal only went along with Alahakoon that night "as a third person, to calm the waters".

While he thought that Alahakoon would lose a fight with the bigger, fitter Mr Battelage, Mr Brandts-Giesen told the jury: "A small man with a knife can easily slay a sleeping giant."

They went to Oxford Working Mens Club to drink and watch a televised game of international cricket before returning to Mr Battelage's house.

After drinking more vodka, Alahakoon - who played senior club cricket with the victim at Oxford - says he fell asleep on the lounge floor.

He claims Sawal woke him shouting, covered in blood, with Mr Battelage lying dead on the couch.

Sawal denies that version, saying he was outside smoking a cigarette when he saw Alahakoon through the lounge window attacking Mr Battelage.

Sawal says he tried to stop the assault and that's how the dead man's blood came to be on his clothing, which was found by police dumped outside a Christchurch red zone property.

The Crown says the movements of Alahakoon and Sawal that night were captured by CCTV and security technology.

Mr Battelage's badly charred body was found by firefighters later that morning.

The pair were soon arrested and charged with murder and arson.

Mr Brandts-Giesen said the Crown's argument that Sawal had a motive to kill Mr Battelage was wrong.

But it correctly summarised the motive for Alahakoon, who was "consumed" by jealousy and after methodical planning had killed his former friend Mr Battelage in a "murderous rage".

Alahakoon is also charged with assaulting a woman, who has name suppression, with a pair of scissors on December 5, 2011, and again on Boxing Day that year.

The trial, before Justice Christian Whata, continues, with Alahakoon's defence team to begin summing up later today.

- APNZ