As police narrowed in on Ms Droudis as a suspect, surveillance recordings captured Monis reassuring her and offering her explanations as to why her hair, skin or blood might be found at the crime scene.

Ms Droudis, 37, is on trial in the NSW Supreme Court accused of stabbing Monis' ex-wife 18 times, dousing her body in petrol and setting her alight in April 2013.

She has pleaded not guilty, although her defence team does not dispute that Monis was the mastermind of the brutal killing outside the apartment he rented in western Sydney.

After a summons was provided to Ms Droudis indicating that she was a key suspect and police wanted to take a DNA sample, Monis was captured telling her not to worry and that there would be no problems.

"One hundred times you have been up and down to my unit," Monis said.

"They found hair at the scene, we say we have another 100 hairs for that."

When Droudis says she once had a fall in the stairwell of the unit and was badly bruised, Monis says the graze was so bad that she bled.

"No I didn't bleed…but maybe my skin would be on there," Droudis says.

"Little bit it did, I remember it," Monis replies.

"Oh yeah, yeah, yeah, yeah, yeah...that's right," Droudis responds.

"I go further than hair and fingerprints….even your blood even might have been there. At the time that you fell it used to be home, second home," Monis says.

Crown prosecutor Mark Tedeschi QC told the court the recordings are evidence of consciousness of guilt, showing the pair "conspiring together to create a false explanation".

"[Ms Droudis] is having this conversation and she is going along with Mr Monis lying about blood having been spilt on another occasion because of her fear that the truth would disclose her guilt," Mr Tedeschi said during legal argument about the recordings.

"Why would Mr Monis be in any way concerned about her DNA and how it got there unless they were co-defenders in the murder?"

Mr Tedeschi also said the pair were aware they were the subjects of surveillance and would intentionally put comments about their innocence "on the record" for police.

Senior public defender Mark Ierace SC said it was unrealistic to conclude they knew they were being recorded, and Ms Droudis would rightly be panicked as an innocent person after receiving the summons identifying her as the key suspect in the murder. His client, Mr Ierace said, also believed Monis was innocent at the time of the conversation.

"If the accused was the killer she would have realised that she didn't leave any blood behind, that she wasn't injured," Mr Ierace told the court.

The recordings also capture Ms Droudis explaining to Monis what the word alibi means and that police believed she did not have one for the day of the murder.

Monis tells her it is "nothing" and suggests her parents might be able to sign something saying she had been at their home on the day of the killing.

"In the future when we decide to talk to [police] then they will understand that you have alibi more than me," Monis says.

"So there's no problem."

The judge-alone trial continues on Thursday.