Stephen Raymond Stubbs, 63, is alleged to have asked for and received $4000 from Legal Aid ACT, a service for Canberrans who cannot afford legal representation, while also being paid more than $30,000 by his client's mother.

Stubbs' charges arise from events in late 2008.

In November that year, Canberra man Alexander Duffy had been arrested and charged with assault and acts endangering life.

The charges were later upgraded to the more serious offence of conspiracy to commit murder, prosecutor Katrina McKenzie told the court in her opening submissions.

Duffy was granted legal aid, and he nominated Stubbs, the sole practitioner at Diana Burns Solicitors, as his preferred lawyer.

Over the course of a year, it's alleged Stubbs received money from both Legal Aid and Duffy's mother, without telling either about the other's funding the matter.

Duffy's mother did not know her son had received the grant, Ms McKenzie said. But over the following year, she gave Stubbs $30,000 in legal fees, including, allegedly, one cash payment.

The prosecutor told the court ACT law prohibits lawyers demanding or receiving outside payments on cases after a legal aid grant.

Legal Aid did not know about the payments from Duffy's mother, Ms McKenzie said. She said Stubbs had approached Legal Aid, complaining about the "incredible amount of work ... with no assistance at all by way of additional funding".

Stubbs engaged Canberra barrister Richard Thomas but failed to tell Mr Thomas that the matter was under a grant of legal aid, the prosecutor told the court.

"Everyone's kept isolated, with the linchpin being the accused," Ms McKenzie said.

She asked for the jury's patience and attention, through what was likely to be a laborious process of going through the evidence of business records, bank statements and emails.

Prosecution witness Mary-Therese Daniel, manager of client services at Legal Aid ACT in 2009, gave evidence on Monday, explaining how the service worked.

She said it relied on lawyers to say what work they were doing and what they did in court.

"It's an honour system," she told the court.

She said it did not surprise her to read an email from Stubbs about the amount of work he was doing under the grant. It was a requirement of the system that lawyers were paid less than a commercial rate, and often in lump sums.

Stubbs' defence barrister Theresa Warwick had earlier told the jury in her opening submissions that there were several extensions to Duffy's original Legal Aid grant.

Ms Warwick said that in May 2009, there was an extension of funding for a further two charges against Duffy relating to an assault in Civic.

She asked the jury to think about what work was covered by which grant. She said it was the defence position that a number of the legal proceedings in which Stubbs appeared were in fact outside the grants of Legal Aid funding.

Stubbs faces 15 counts of dishonestly obtaining property by deception - three counts as against Legal Aid and the rest against Duffy's mother.

The trial continues before Justice John Burns.