The former patrol commander codenamed Person Five is due to return to the Federal Court on Friday after giving two days of evidence in Mr Roberts-Smith's defamation case against three newspapers.
Person Five denied a key accusation put to him by the newspapers' barrister Nicholas Owens SC that he ordered a young trooper to execute an unarmed prisoner during a mission dubbed Whiskey 108.
This was said to "blood the rookie" so the new recruit could get his first kill.
"We don't blood people, I thought I made that perfectly clear," he said.
Mr Owens submitted that Person Five could not change his story and confess because it would place his friend and second in command Mr Roberts-Smith in an impossible position.
"Why would I confess to something that never happened," he replied.
The former Royal Marine said he was disappointed to read "lies" surface in 2018 media reports after his comrades spoke to journalists.
"I don't think SAS members should speak to anyone about anything ... (they) should be gone, should be sacked."
Mr Roberts-Smith is suing The Age, The Sydney Morning Herald over reports claiming he committed war crimes in Afghanistan including murder, and acts of bullying and domestic violence.
The 43-year-old denies all claims of wrongdoing, while the mastheads are defending them as true.
Person Five on Thursday said he warned Mr Roberts-Smith that the probe into Afghanistan by the Inspector-General of the Australian Defence Force was a witch hunt that he should prepare for.
He also admitted under immunity that he sent Mr Roberts-Smith confidential information pertaining to evidence he had given during his interview with the IGADF.
He wanted to complain about the treatment they were facing, and was seeking legal advice, he said.
Person Five said he discovered on Tuesday that all his legal fees had been paid for by Seven Network, and had never made any inquiries as to rates, bills, or estimates of costs prior to that day.
The trial before Justice Anthony Besanko continues.
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