A medical examination the next day showed his death was probably due to a cardiac arrhythmia.
Mr Peebles' obesity, diabetes and a potential interaction between two drugs he had been prescribed may have contributed to the death, the doctor reported. The level of both drugs appeared to be consistent with normal use.
His family did not want him to have a full post-mortem examination as they said he had been through enough in his life. Because of that Mr Matenga said it was hard to give an exact cause of death.
Police were satisfied there were no suspicious circumstances.
Mrs Spence told the inquest she thought there was a "systemic failure on the part of those looking after chronic mental health patients in our health system".
"I think for someone who has been known to psychiatric services since teenage years and has been on big doses of drugs for the last 10 years solidly, being a registered nurse, I found it completely shocking that there was not an ECG," she said.
Mr Matenga said that was also a point raised by the doctor that examined Mr Peebles' body.
Mrs Spence said she thought he would have had regular check ups.
"I think in regards to his physical health for a long term patient such as him, I think they could do a much better job."
Mr Peebles' mother Kathleen Peebles told the inquest the last time she visited her son was two days before his death, when she gave him a back massage as he was in pain.
"He wasn't in high spirits, he was in very low spirits... he looked to me very sad and he wasn't as jovial as he normally is," she said.
Mrs Peebles said he was her youngest child and he had a long history of mental illness.
"The biggest issue for me was the state of his long-term mental health and the lack of health checks on his body because of the issues that he suffered from taking medication.
"I think that because he was a client with no huge drug, alcohol issues he just kind of rolled through the system year after year and because he didn't cause huge problems I think health checks were not completed like they perhaps should have been."
She said she had lived with her son for the past three months of his life and she had noticed changes in his physical health.
After the inquest Mrs Peebles told the Rotorua Daily Post her son had grown up in Ngongotaha and was a happy-go-luck sporty boy who enjoyed basketball and rugby.
She said it wasn't until the age of 19 that he started to struggle with mental health issues.
Mr Matenga offered his condolences to the family and reserved his findings.
