An electronic crime expert has begun giving evidence in the trial of South Australian MP Bernard Finnigan, who is charged with child pornography offences.

The former police minister is charged with obtaining access to and attempting to obtain access to child pornography.

Finnigan has pleaded not guilty to the charges.

Electronic crime expert Robert Taylor - a senior electronic evidence specialist employed by South Australian Police - will be the only witness called to give evidence at the trial.

The trial begins four years and around 30 court hearings since Finnigan was arrested in April 2011.

The 42-year-old was charged after police raided his Sefton Park home and seized two of his laptop computers.

The trial without jury is being heard by Judge Steven Millsteed in Adelaide's District Court.

Prosecutor Mark Norman told the court Finnigan had entered terms into a search engine which took him to several child pornography websites which he clicked on.

He said that happened both in December 2010 and April 2011 and the terms involved "obvious connotations of child sex".

Mr Norman said his searching and viewing of the sites showed a pattern of conduct that defied any suggestion that his access was accidental.

He said the pattern of behaviour started on December 7, 2010, when Finnigan had entered a term into a search engine.

"The prosecution says that term was specific and unambiguously to do with child sex," Mr Norman said.

Mr Norman told the court the charged offences occurred on December 24, 2010 and April 12, 2011.

"In fairness to the accused, he certainly did not spend hours (on the sites). It was probably about three minutes, yet he still had plenty of time to see and realise what was on the screen," he said.

"The fact that he continued to look at these sites, rather than simply close them down as he might have done if this had been some terrible mistake, is particularly relevant.

"This might be called furtive rather than brazen, but it is deliberate even if he only did so for one minute."

Trial listed for several days

Defence counsel Michael Abbott said the issues at trial would be Finnigan's intent and what the terms 'obtaining access' meant under the law.

"Most of these websites were open only for seconds not minutes," he said.

"(The prosecution's) version is that obtaining access is going to a website that may contain child pornography.

"We say obtaining access involves viewing child pornography and the words "obtaining access" need to be given appropriate weight, given their role in the legislation."

The trial is listed to run for five days but the court heard it will likely be condensed because a number of the facts have been agreed and only one witness will be called.

The court has been closed for Mr Taylor's evidence, much of which Mr Norman said was "sensitive", because it will be shown the websites.

Finnigan quit the Labor Party soon after his arrest but has continued to sit in State Parliament as an independent.