A mother who admitted she was an alcoholic who smoked P and marijuana around her two year old son, blew cannabis smoke in his face and waited for days to take him to hospital with a broken arm, has denied any role in his death.

The defence in the JJ Lawrence murder trial showed its hand yesterday suggesting his mother Josephine Lawrence confessed to killing her son.

Lawrence, 27, endured a gruelling cross-examination yesterday in which it was put to her that she had confessed to her murder-accused partner Joel Loffley that ''I did it''.

JJ LAWRENCE: The two-year-old died at his home in Auckland in November 2011.

She denied she said it but admitted a conversation in which she told Loffley she had discussed with family that ''she might get five or six years because it was an accident''.

She later said what she meant was that she felt guilty because she was JJ's mother and she should have been looking after him the morning he died.

Loffley is charged with murdering JJ by striking the two-year-old in the stomach while his mother was out, causing his internal organs to rupture, on November 14, 2011.

Defence lawyer Roger Chambers put it to Lawrence that she had gone to bed with Loffley the night after JJ's tangi and talked about ''a guilty plea and hurry up and get it over with''.

Lawrence said the conversation centred on Loffley's involvement rather than hers.

''I asked him what happened to JJ. I told him I thought he did it. He asked me do you think I did it. I said 'yes'."

Earlier in the cross examination, Lawrence admitted she was an alcoholic who smoked P and cannabis around her son at their Orakei, Auckland home.

She also admitted she did not take the boy to a doctor for several days after he broke his arm because she was drunk and she was scared the boy would be taken from her.

Lawrence had testified that Loffley forced JJ to smoke marijuana through an asthma inhaler.

However, she admitted getting ''wasted'' a lot and sometimes blowing cannabis smoke in JJ's face herself.

''I probably used to blow some in his face but he used to give him full on spots,'' she said of Loffley.

Lawrence said she took drugs and drank a lot but all the drugs came from Loffley's friends and she usually had a babysitter.

She sold cannabis tinnies to her friends but insisted that it was Loffley's ''shop''.

Chambers put it to her that Loffley had offered to call an ambulance after JJ suffered a broken arm for a second time.

Lawrence said she was testifying behind a screen that prevented her from seeing Loffley because she did not want to be intimidated by the accused.

However, Chambers put it to her that she had had a lot of contact with Loffley since he was charged including writing him hundreds of letters and a Valentines Day card, giving him money every week and providing him with shoes and a watch.

"I supported him because he said he didn't do anything and I believed him.''

When Loffley's violence towards her was questioned, particularly why she did not leave him or get help after he allegedly strangled her, she said: ''I loved him at the time. I was dumb. Love makes you do crazy things.''

The trial continues.