Eddie Obeid "duped" a senior bureaucrat in the state maritime authority and was acting in his own interests "under the cloak" of representing constituents at Circular Quay, the Crown has told the jury in the former Labor MP's criminal trial.

Crown prosecutor Peter Neil, SC, said in his closing address to the jury on Wednesday that Mr Obeid failed in his "duty to act in the public interest and only in the public interest" and should be convicted of misconduct in public office.

Mr Obeid, supported in court by his wife and daughters, has pleaded not guilty to the charge.

The jury is expected to begin its deliberations as early as Friday.

The Crown alleges Mr Obeid "intentionally deceived" Steve Dunn, then deputy chief executive of the NSW Maritime Authority, "into assuming he was acting...for arm's length constituents" when lobbying Mr Dunn in 2007 about the plight of retail tenants at Circular Quay.

In fact, the Obeid family had a financial interest in two cafe leases on wharves four and five at Circular Quay and they were seeking a renewal of those leases without competing in a competitive tender.

A public tender posed a "very real risk" to the family's investment in the businesses and "something had to be done", Mr Neil submitted.

The court has heard an "agitated" Mr Obeid called Mr Dunn in August 2007, two days after he started as deputy CEO of the maritime authority, and asked him to meet a commercial negotiator acting for a group of disgruntled tenants.

He did not reveal the negotiator was also acting for a company linked to his family.

The leases were subsequently renewed without a tender in January 2008.

Mr Obeid and Mr Dunn had worked together when the former was fisheries minister and the latter was the director-general of the fisheries department.

Mr Dunn had a "high regard for Mr Obeid", Mr Neil said, and considered him a mentor and "someone who had the capacity to promote Mr Dunn's career".

"The accused would have known that in contacting Mr Dunn he was contacting someone ... likely to do what he asked without question," Mr Neil said.

Mr Neil said Mr Obeid's failure to disclose his family's interest to Mr Dunn "had to have been deliberate".

It was "very serious" that an upper house MP would go out of his way to deceive a public servant "to benefit his own private interests", he said.

Damian Obeid, the eldest of Mr Obeid's five sons, gave evidence at the trial that he did not not recall discussing business matters with his father.

He said his father was "very busy" with parliamentary duties and handed over the running of family businesses to his sons after he entered parliament in 1991.

But Mr Neil said the suggestion Mr Obeid snr was in a "vacuum or cocoon" of parliamentary duties did not make "any sense at all".

The family home, Passy in Hunters Hill, was mortgaged to purchase the cafe leases and Mr Neil said "significant cash payments" from the cafe's tills were given not only to Mr Obeid's wife Judith for "housekeeping" but also to Mr Obeid over a number of years.

The defence has insisted Mr Obeid did not receive money directly from the cafes and had only an indirect interest in the businesses via a family trust.

Defence counsel Brad Hughes, SC, will deliver his closing address to the jury on Thursday. Justice Robert Beech-Jones will then deliver his summing up.