The Crown says a man killed and buried his then partner and her daughter because he was jealous after she had left him.
But Kamal Gyanendra Reddy (42) has repeatedly denied murdering Pakeeza Yusuf and her three-year-old daughter Juwairiyah "Jojo" Kalim.
The pair were found buried under the Takapuna overbridge in Auckland in October 2014 but the Crown says Reddy strangled the adult victim, then smothered her child with a pillow at the end of 2006 or early 2007.
The corpses were only uncovered when the defendant made admissions to undercover officers after an extensive six-month operation to gain his trust.
Reddy this week opted to give evidence and told the jury the murders were actually committed by a man called James, who was in a relationship with Ms Yusuf at the time of her death.
His only role was to suggest a location where the bodies could be hidden, he said.
"I'm going to suggest you were jealous of Pakeeza. She was a very beautiful woman and you didn't want her seeing anyone else," Crown prosecutor Natalie Walker said.
"I'm going to suggest you were resentful of her because you paid money to get the flat in Howick and on the night in question, she wouldn't let you in."
Reddy said that was "not true".
In all recorded conversations between the defendant and undercover officers, there was no mention of James but today he claimed he had raised the name.
"Even though the name's not anywhere in the transcripts or the audio or the DVDs," Ms Walker said.
The prosecutor took Reddy through several secretly-recorded conversations in which he said he had punched Ms Yusuf and fallen out with her after she made a scene at a family gathering.
He told the court today it was "all lies".
Reddy said he posed as the killer because he believed the undercover officers could help him, and subsequently James, avoid arrest.
Earlier this week, the 42-year-old told the jury James came to his home in Otahuhu one night to confess he had killed Ms Yusuf and Jojo.
James allegedly enlisted his help by threatening Reddy that if he did not, his friends would come after him.
Defence lawyer Jonathan Krebs said his client was pressured into making a confession by incessant questioning by undercover police and only knew about the burial site because his uncle Bal Naidu had suggested the area.
