A Christchurch man who police suspect took his own life may not have killed himself, a coroner has found.

Philip James Nisbet, aged 47, was found dead in his home May 4 2009 and police ruled there was no evidence of foul play, Fairfax Media reported.

However, coroner Sue Johnson, who held an inquest into the death in November, found there was insufficient evidence that Mr Nisbet killed himself.

There was no "evidence of any weight" that he intended to commit suicide and there was "no objective proof" he was the author of two suicide notes, which were sent by text and typed on a computer.

Mr Nisbet's widow, Helen Nisbet, who was the last person to see him alive, showed police a text sent from her husband's phone at 10.30pm which included the words "i can't keep going like this".

She also showed police a computer written suicide note she found on a piece of paper in a briefcase, which had her husband's name typed at the bottom.

Mobile phone records showed she had sent a friend a text message about the suicide note six weeks before telling police.

Mr Nisbet's family said they were shown a note which was signed with handwriting and not typed.

Coroner Johnson said Mrs Nisbet's evidence was inconsistent and she was an "unreliable witness".

She said other than the fact the text message was sent from Mr Nisbet's cellphone, there was "no evidence to indicate he sent it".

The threshold of evidence for suicide had not been met, and "I leave this point open", the coroner said.

Mr Nisbet's adopted sister, Lee-Anne Cartier, said the findings showed police had "messed up" the investigation into his death.

Detective Sergeant Scott Anderson said there were no plans to reopen the case.