Tan Sri Muhammad Shafee Abdullah said Datuk Shahrol Azral Ibrahim Halmi had consistently said that Najib was close to Low and therefore knew about the fugitive businessman's plans to defraud 1MDB.
However, he said, Shahrol who trusted Low, had made all the decisions which backfired on 1MDB.
"My client is not the professional who managed the fund..it is Shahrol who was the professional..he was the CEO of 1MDB.
"He is now saying that he was not suspicious of Low and trusted him.
"If he can claim lack of knowledge, my client's position was even more difficult. I want to make him swallow his own vomit," he said.
Shafee said this after he was asked to explain where he was going with his lengthy cross examination of the prosecution witness, who has been on the stand since September.
Lead prosecutor Datuk Seri Gopal Seri Ram had earlier stood up to query Shafee's repeated bombardment of the witness with one document after another on various transactions which had taken place involving 1MDB and its joint venture partner, PetroSaudi International Ltd (PSI).
Shafee replied that he had taken great pains to adduce the documents for Shahrol to reconfirm or refute evidence which was different from his interpretation of things.
"It would have alerted any CEO as the transactions involved not millions but billions of US dollars..yet he keeps saying that he acted without knowledge of the truth.
"All because he trusted Jho Low," he said.
Earlier, Shafee also put Shahrol under the hammer over how 1MDB had transferred US$1 billion to Low's company (Good Star Ltd), instead of PSI.
He chided Shahrol how 1MDB seemed to be making mistake after mistake even when handling huge sums of money.
Shahrol admitted that 1MDB had transferred the money into Good Star's account even though the beneficiary in the remittance forms was listed as PSI.
The first transfer of US$700 million via Deutsche Bank was done in Sept 2009, while another transfer of US$330 million was done via Ambank in May 2010.
Shahrol said he did not suspect that Low owned Good Star at that time.
"There was no reason for me to be suspicious then..it was just an account number given to us by a trusted partner.
"I did not memorise their account number," he said.
Shafee: But you were sending a lot of money..it was not in the bracket of millions but billions. It looks like you were negligent. You did not even check the account number of the recipients.
Shahrol: I disagree.
Shafee: There was no diligence on your part, or your team.
Shahrol: I disagree.
Later, Shahrol said he had queried Low about Good Star but the latter denied that the company belonged to him.
"He told me PSI will explain everything and they sent me a letter to explain that Good Star was indeed affiliated to them," he said.
However, Shafee then read out the contents of the letter and said: "It was a very calculated, limited answer which is clinically correct but morally wrong."
Today's session ended with Shahrol revealing that 1MDB eventually ended up giving away US$1.83 billion to PSI after entering into a joint venture with the company and the murabaha financing agreement.
The trial before justice Collin Lawrence Sequerah will continue on Monday.
Najib, 66, is facing 25 charges of money laundering and abuse of power over alleged 1MDB funds. He is accused of abusing his position to obtain RM2.28 billion in bribes in February 2011 and December 2014.
He is also alleged to have transferred RM2.28 billion in illegal funds to his bank accounts and subsequently using the money.