For a brief moment on Tuesday morning, Lois Greste struggled to hold back tears when talking about her son Peter.

Her husband Juris placed a comforting arm around her shoulder as she regained her composure.

It was a rare moment of insight into the emotional turmoil occurring behind the closed doors of the couple's home in Brisbane's south-west, since their son was detainedin Egypt in late December.

For six months, the couple has regularly faced the media, stoic in the face of repeated judicial setbacks that have kept Peter Greste, an esteemed journalist with Middle East-based broadcaster Al Jazeera, and two colleagues in prison.

The trio was found guilty of spreading false news and assisting the Muslim Brotherhood.

''This man, our son Peter, is an award-winning journalist, he is not a criminal. He is not a criminal,'' Mr Greste said on Tuesday, less than 24 hours after learning of his son's seven-year jail sentence. ''Journalism is not a crime.''

It was an obviously deflated Mr and Mrs Greste on Tuesday morning. ''Shattered'' was the word Mr Greste used to describe his family, and the couple's demeanour supported the description.

While Mr Greste affirmed the fight to free their son would continue, because ''there is no choice'', it lacked the conviction it once had.

Despite all assurances they had received prior to Monday that justice would prevail, the reality was resoundingly clear.

Their son was caught in the middle of an international incident, over which no one outside Egypt had any control.

Mr Greste said the thought of the squalid prison conditions his son was enduring escalated his family's concern.

Until now, Mr Greste said, his son and his colleagues had been held in a maximum security, four-by-three metre cell under the domain of Egyptian prosecutors.

''It is true, our first and immediate concern after his arrest was to get Peter out,'' he said.

''[But] to us, it is not just affecting the greater family … it is also a slap in the face and kick in the groin to Australia, as well as all fair-minded people across the world. The campaign for media freedom and free speech must never end.''