Duffy had pleaded not guilty to 31 charges, including several that involve travel to Conservative party events which he in turn billed to the Senate.
The AG's report, a copy of which was viewed by The Canadian Press, provides definitions that were used as criteria by auditors who scrutinized the books of individual senators.
The definition of parliamentary functions reads, "Duties and activities related to the position of senators, wherever performed, and includes public and official business and partisan matters..."
Public business is defined as including "official business, representative business, partisan business and related travel, but does not include attending to one's private concerns."
The only areas specifically excluded are activities related to getting a person elected to the Commons, and to the private and personal business of a senator.
Duffy's participation in political events would often dovetail with personal visits he had also arranged.
Of the 30 senators who have been singled out as having questionable expenses in the auditor general's report, none appear to have been engaged in specifically partisan travel.
The contents of the auditor general's report will be closely examined by the players involved in Duffy's trial, as well as lawyers representing suspended senators Mac Harb, Pamela Wallin and Patrick Brazeau.
Duffy has pleaded not guilty to 31 charges of breach of trust, fraud, and breach of trust in relation to his Senate office, living and travel expenses.
His lawyer Donald Bayne has pointed to the Senate's own rules as justifying travel to partisan events.
The Senate changed its travel policy in 2012 to include a specific list of types of activities that were not to be covered by the public purse.
The court heard Monday from Duffy's former executive assistant Melanie Mercer, a former political staffer who wound up working for Duffy from his appointment in 2009 to his suspension in 2013.
Mercer came across through the prosecution's examination as a loyal employee who followed Duffy's instructions and directions unquestioningly.
"I did as I was asked to do, I did as I was told," Mercer said.
She explained how in her early days working in the Senate, she had two women from other senators' offices help show her the ropes. One of their suggestions was that Duffy pre-sign stacks of travel claims to make things more efficient.
"He was also very high in demand and he would be travelling quite a bit," Mercer testified.
"When these ladies suggested this method of filing and having these pre-signed forms at the ready, it just seemed like a good idea at the time."
Crown prosecutor Mark Holmes asked Mercer to review some of the travel forms she had filled out, including one in which Duffy appeared to be travelling in order to attend a medical appointment.
She testified that she completed the paperwork based on information Duffy would give her, or else information he had logged in his daily calendar.
Holmes also took Mercer through office contract invoices that she helped to file.
The Crown has laid out previously the details of how Duffy arranged $65,000 in contracts to be paid to friend Gerald Donohue. Donohue in turn issued cheques to a series of service providers, including speechwriters, an office volunteer and a personal trainer.
When Mercer was told the names of some of the providers, she said wasn't familiar with all of them.
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