Jack Steven James Brearley, 24, told a jury that prosecutors had it wrong and he did not strike Cassius Turvey in the head with a metal pole in Perth's eastern suburbs on October 13, 2022.
After taking the stand on Thursday, he said his co-accused, Brodie Lee Palmer, 29, swung the blows that led to the 15-year-old Noongar Yamatji boy's death in hospital 10 days later.
He also denied being in an alleyway next near where he lived when shopping trolleys were allegedly pulled apart to create makeshift weapons.
But he was forced to concede he was after Palmer's lawyer, Christian Porter, showed him CCTV footage during cross-examination.
Brearley said he was doing a drug deal but he denied that he carried a small axe into the alley to break up a shopping trolley.
"I'm not going to openly walk out the house and show the camera that I've got drugs in my hand," he told the Western Australian Supreme Court on Friday.
"It could be a bag of weed."
A further video showed Brearley coming and going from the alleyway.
"I could have got something wrong and have to go sort of that inside then come back out," Mr Brearley said.
Mr Porter said it was "total nonsense".
"You're there breaking poles off in the alleyway," he said.
"You're not doing customer service for someone who's just purchased your drugs."
Brearley denied he lied to the jury in his earlier evidence.
Brearley's girlfriend Aleesha Louise Gilmore, 23, and one of his co-workers, Mitchell Colin Forth, 26, are also are on trial for the murder of Cassius.
Mr Porter also played a video in which he alleged Brearley was speaking to Gilmore's mother after Cassius was allegedly attacked.
A voice can be heard saying: "He was laying in a field and I was smacking him with a trolley pole so hard."
Brearley denied it was him. He also denied mocking Cassius when the voice mimics the teen saying, "I'm so sorry, don't hurt me."
"The person at the other end of the call is a voice that sounds remarkably like yours," Mr Porter said.
But Brearley agreed there were inconsistencies with his defence story relating to his assertion that he had a physical altercation with only one person that day and that person was Cassius.
Brearley's evidence was that Cassius was wearing a green shirt and the teen had slashed him with a knife during a scuffle in the bush.
But Mr Porter took him to previous statements to police where he said the person with the knife was a "big Kiwi fella" with a blonde rat's tail and wearing a grey shirt.
Another was his evidence that he only punched Cassius twice in the head and the blows caused a cut to the teen's eyebrow.
Brearley agreed multiple witnesses involved in Cassius's medical treatment had not seen or recorded the injury.
Brearley's descriptions to the jury and police of the location where he said his fight with Cassius happened were also inconsistent.
Mr Porter said a further problem for Brearley was the "sheer weight of eyewitness evidence" that a "skinny man" caused Cassius's fatal injuries.
"Evidence about you hitting Cassius with a pole," he said.
"That is a problem for them, but it's not what happened," Brearley replied.
"You are lying through your teeth," Mr Porter said.
"You is you have transplanted Cassius into the real scenario and pretending that is where the story stopped but what actually happened is that you were stabbed and lost it is you moved on to the next kid.
"That boy slower and an easier mark ... and unarmed and like every violent bully in history you've taken you frustration and rage on the easier mark who was Cassius Turvey and you did it with a trolley pole."
"I disagree," Brearley said.
The trial continues.
13YARN 13 92 76
Lifeline 13 11 14
