Margaret Anne Otto, of Risdon Vale, and Bradley Scott Purkiss, of Elderslie, are jointly charged with the 2016 alleged murder of Ms Otto's husband Dwayne Robert Davies.

The pair have pleaded not guilty.

In a interview with police on May 30, 2017, four days after Mr Davies was last seen, Ms Otto said she did not tell her co-accused Mr Purkiss to kill her husband.

A video of the six hour and 10 minute interview was played for the jury.

"I didn't know he was going to kill him until after it was done," Ms Otto said in the video.

"There was no calculated plan.

"I did not have anything to do with the killing. I did not move the body."

Ms Otto said Mr Purkiss had not told her where the body was.

"He just said he would never be found," she said.

"[He said] you need to know nothing."

Earlier in the interview, Ms Otto detailed her former affair with Mr Purkiss and told police how she would confide in him about her issues with Mr Davies.

Ms Otto said she had told Mr Purkiss it would be easier if her husband was dead.

"He's taken that as this is what I actually want," Ms Otto said.

"I didn't want him murdered.

"I wanted him out of my life - I didn't want this.

"I feel so accountable that I might have actually caused it.

"If I hadn't said anything would Brad have gone to such extremes to protect me?"

Ms Otto said when Mr Purkiss visited her at her workplace the day Mr Davies disappeared he asked her if she was ready to "get out" of her marriage.

"He said 'if you don't make a decision I will make it for you'," she said.

Ms Otto told police Mr Purkiss came to see her again that day, arriving at her Risdon Vale home with Mr Davies' phone and keys at 11pm.

She said Mr Purkiss put a bullet cartridge down on the bench and told her "you're free. He's never coming back."

Ms Otto said she regretted lying to police and not coming forward sooner with this information about Mr Purkiss following Mr Davies' disappearance.

"I've obviously f--ked that up," she said.

"Why, why didn't I say something about it when I realised? Is it because I was relieved?"

The trial before Chief Justice Alan Blow continues.