Sofia, Bulgaria: A young Australian facing jail on terror charges in Bulgaria had vehemently rejected Islam more than a month before his arrest, according to evidence seen by Fairfax Media.

Former Sydney schoolboy John Zakhariev, 21, could be sentenced to up to eight years' jail for allegedly training in Bulgaria with the intention of joining Islamic State.

Though no verdict has yet been reached, his lawyer said on Tuesday he was "not hopeful" of an acquittal.

A Bulgarian judge has refused to consider the evidence, saying on Tuesday she had heard all she needed to reach a verdict.

But days before Mr Zakhariev's arrest last September, he sought advice from a former devout Muslim who now writes a blog called "My Journey from Islam", explaining his reasons for rejecting the faith.

"Islam is nothing more than Arab supremacism," Mr Zakhariev wrote privately to Canadian blogger Abdullah Sameer, in a long essay he titled Notes on Islam.

His long, theologically dense essay criticised jihadist doctrine – in particular the anti-Western, Islamist beliefs of Hizb ut-Tahrir.

Zakhariev was disappointed in what he saw as inherent racism in Islam and preferred "humanism or liberalism which holds that all men are equal and no race is better than another".

Mr Sameer provided Fairfax Media with the original Word document that Mr Zakhariev sent him. The metadata in the document shows that it was created on August 18, 2016, by John Zakhariev of Waverley College.

Mr Zakhariev graduated from Waverley College in 2012. He was arrested in Bulgaria on September 20 and charged with undertaking firearms training with the intention of committing a terrorist act. He was said to have practised firing weapons including a Kalashnikov at shooting ranges in Sofia, Plovdiv and Voyvodinovo.

According to the indictment, Mr Zakhariev had intended to leave the country and carry out a terrorist act. But a week before his arrest, Mr Zakhariev had contacted Mr Sameer over the internet, describing himself as "an ex-Muslim too, as someone who was involved in Dawah [proselytising]".

Mr Zakhariev had joined the Street Dawah group in Sydney in 2013, led by Mohammad Ali Baryalei, who went on to become a high-ranking IS recruiter.

Mr Zakhariev asked Mr Sameer to post videos "about the many scientific errors in the Quran", saying "voices like yours need to make themselves heard, especially with so many Dawah [propa]gandist[s] around today".

Mr Zakhariev asked if there were "many ex-Muslims" in Canada, and complained "I don't know any".

The next day he sent Mr Sameer his essay. Mr Sameer, who ran a popular Islamic website before he left the faith, told Fairfax Media it was clear Mr Zakhariev "had a lot of doubts about Islam", and sounded genuine.

He had replied to the young man's email, praising the essay, but the reply bounced.

On Tuesday, Mr Zakhariev's lawyer tried to show a Bulgarian court evidence about his client's exchanges with Mr Sameer, as proof his client had rejected Islamist doctrine.

However, after hearing evidence from a computer expert who couldn't find traces of the exchange on Mr Zakhariev's laptop, judge Biljana Vrancheva declined to review other evidence of the exchanges, saying they weren't legitimate.

Mr Zakhariev said the court's refusal to hear the evidence "shows what kind of a justice system there is in this country and what kind of trial I'm facing".

The prosecution and defence are due to make their closing submissions on June 5, followed by the court's verdict.