The body of a man who was haunted by the unsolved rape and murder of his mother and sister 30 years ago was found decomposed in his Wycombe flat earlier this year, an inquest heard.

Justin Tapp suffered from depression and was diagnosed with post-traumatic stress disorder (PTSD) four years ago following the "traumatic events" of his childhood, in which his mother and sister were raped and killed in Australia when he was just 14 years old.

Buckinghamshire Coroners’ Court heard today how the 44-year-old had problems with alcohol and had tried several times to commit suicide.

A substance called potassium formate was found at Mr Tapp's West Wycombe Road ground floor flat after his body was discovered on June 3.

However, due to the level of decomposition, assistant coroner Crispin Butler gave an open verdict, with the cause of Mr Tapp's death unable to be unascertained from the postmortem.

Mr Tapp's former girlfriend, Wendy O'Donovan, spoke at the inquest this morning and described him as a deeply "religious" and "soulful" man.

Ms O'Donovan said the person responsible for the murder of Mr Tapp's sister and mother was never brought to justice and that every ten years, a journalist writes an article about the unsolved case.

She said: "One of our last conversations we were talking about Andrew (the journalist) coming over. He didn’t know if he could handle it.

"He used to talk very, very deeply due to what happened to him. One of the things he talked about was a peace pill."

Near Mr Tapp's body, police found a book detailing suicide methods, as well as the legal and moral aspects of taking one's life.

Potassium formate was in the kitchen bin at Mr Tapp's flat and a mug was found with white residue on it.

Ms O'Donovan said the pair had spoken about the pill.

She added that Mr Tapp used to drink and had been known to go on binges lasting three or four days.

When she had not heard from him in a few days she thought he was "on one of his binge drinking sessions".

The inquest heard that, due to the level of decomposition, it was impossible to tell exactly when he died, although taking into consideration neighbours' accounts, it is estimated he might have died on May 29 or 30.

Mr Tapp had no family living in the United Kingdom and it was after one of his aunt's contacted Ms O'Donovan that his friend of many years went to his flat.

Ms O'Donovan peered through the window and thought she saw him collapsed on the floor. 

Police and paramedics were called to the West Wycombe Road flat at about 8pm on June 3.

After forcing entry to the house, police found Mr Tapp face-down on the living room floor.

Mr Butler said there was a "significant element of decomposition", making it difficult to identify the medical causes of death.

He said that Mr Tapp had lived a "traumatic life", but there was not enough evidence to conclusively say he intended to take his own life.

He said: "Sadly in some situations the conclusion is unsatisfactory", adding: "We will never know the circumstances."

An open verdict was recorded.