This week, toxicologist Dr Dimitri Gerostamoulos gave evidence in the trials of Ms Kelly’s housemates Christine Ann Lyons and Ronald Lyons, who are each charged with murder and attempted murder.

Prosecutors argue the two accused plotted with former partner and housemate Peter Arthur to first kill Ms Kelly by drug overdose, and when this was unsuccessful, Arthur killed her with a hammer.

Ms Lyons and Mr Lyons have each pleaded not guilty to both charges.

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The court heard seven drugs were found in Ms Kelly’s system, including four sedatives – two of them Phenergan and temazepam - paracetamol, an anti-nausea medication and a heart medication

“These drugs are not a combination of drugs that will be taken by an individual,” Dr Gerostamoulos told the court.

The court heard that prescribing records indicated four of these drugs were prescribed to Ms Lyons, while Ronald Lyons had been prescribed and supplied a medication with paracetamol and codeine in February 2015, and Peter Arthur had been supplied with paracetamol only in June that year. 

Dr Gerostamoulos said three of the drugs were detected in samples of Ms Kelly’s liver, which indicated they were taken 24 to 48 hours prior to her death.

He said the absence of the other four drugs from the liver samples might have been the result of decomposition.

Under cross-examination, he said he could not comment on the concentration of drugs – whether they were toxic or therapeutic - due to decomposition.

Dr Gerostamoulos also said he was unable to comment as to whether the drugs had been taken together or separately.

Ms Lyons’ lawyer Peter Kilduff asked him if it was true that traces of drugs found in the hair samples of Ms Kelly could indicate they were in her system longer than the 24 to 48 hours he had previously suggested.

“Yes, it may be that these drugs were consumed on previous occasions, I can't rule that out but given the degree of decomposition and the fact that the hair has come into contact with these fluids, it could be that they're contaminated,” Dr Gerostamoulos said.

The court also heard from Ms Kelly’s brother Michael, who described Ms Kelly’s learning difficulties, and how she was a “loving, doting mother”.

Mr Kelly said his sister regarded Ms Lyons as a good friend when she decided to move to Bendigo.

“Chrissy was an awesome friend, mate, and she was always helping her out with the children, is what Samantha had said,” Mr Kelly told the court.

He said that in mid-December 2015 he received a phone call from Ms Kelly, in which she told him “They're starting to take over”.

The court heard that after Ms Kelly’s disappearance, Mr Kelly’s partner began calling numbers she had contacted them on, and the man who answered denied knowledge of Ms Kelly.

He said a person he believed to be Ms Lyons then came to the phone, and on loudspeaker, he heard her talk about Ms Kelly seeing a drug dealer and using drugs.

“I didn't believe it, my sister never touched drugs, um, I'd never actually even seen my sister drunk,” Mr Kelly said. 

He told the court she also said that Ms Kelly changed the names of two children to the names Ms Lyons liked, because she wanted to get back at their fathers.

But he said his sister would not have changed the children’s names.

Mr Kelly said she told them his sister had walked out at 3am, saying she could not do it anymore and the children were hers.

During cross-examination by Mr Kilduff, Mr Kelly told the court his sister’s former partner in Ballarat had assaulted her and taken her money, and she feared for her safety.

He also said there were no conversations with Ms Kelly about a falling out with Ms Lyons.

Mr Kelly’s partner Danielle Stevenson told the court Ms Kelly had said she was moving to Bendigo because she thought it would be a safe haven.

Around Christmas that year, she said, Ms Kelly called her and wanted to visit for a holiday, telling her she felt she had outstayed her welcome.

Ms Stevenson said she spoke to her again in January and she was “really pushing” to visit and get away.

Mr Kilduff asked her if it could have been that Ms Kelly simply wanted a holiday, to which she replied that with Ms Kelly having four children and living with other people, they could understand why she might have felt she had to get out.

The court also heard that The Age journalist Tammy Mills, who reported on Ms Kelly’s disappearance, was told by Ms Lyons on February 11 2016 that Ms Kelly had left.

The court was told that Ms Mills had also said in a statement that Arthur had told her “that Samantha had woken Christine up at 2.30 am to 3 am on 23 January 2016 and said that she'd had enough and then left".

This week saw the cross-examination of Arthur continue. 

Ronald Lyons’ defence lawyer Jarrod Williams took Arthur through untruthful information he had given during the course of the investigation.

Arthur agreed he had thought it would be better for him if he lied and said the murder was in self-defence.

“You thought it might be better for you if you deflected some blame from yourself, put some blame on some other people, didn't you?” Mr Williams then asked, but Arthur rejected this suggestion. 

He told the court that as Ms Lyons’ carer, he did have access to her medications, and he did go with her to a doctor’s appointment and pharmacies with her shortly before Ms Kelly’s death.

He rejected Mr Williams’ proposal that Mr Lyons had never gone out to the unit where Ms Kelly was killed.

The trials continue.