Former Sydney detective Christopher Laycock has been jailed for seven-and-a-half years for crimes he committed nearly 10 years ago while in the police force.

Laycock pleaded guilty to five charges of theft and corruption, including aggravated break and enter, unlawfully accessing a police computer with intent to steal, corruptly receiving a benefit as reward for providing police information and lying to the Police Integrity Commission (PIC).

The former detective sergeant also admitted to four other matters including obtaining $11,000 by deception when he went into a man's house to steal but pretended to be on police business.

In sentencing Laycock to prison with a non-parole period of four-and-a-half years, Judge Jonathan Williams said the former cop had used his "position and power" to commit serious criminal offences.

"He had no entitlement to operate in that way," the judge said in the Downing Centre District Court.

He said Laycock had committed a "twofold breach of trust" by breaking his own rules as a police officer as well as betraying community expectations of the force.

Laycock joined the service in 1989 and was sacked in 2004 after a PIC hearing revealed he and others had been involved in a series of thefts and extortions.

They included receiving $3,900 when he tipped off a doctor who was being investigated over a child pornography network.

He advised the doctor to cleanse or get rid of his computer and dispose of his credit cards and told him how to conduct himself if interviewed by police.

The doctor was never charged with any offence.

Judge Williams said Laycock's actions in relation to that incident had frustrated police investigations into what could have been potentially "very serious" offences.

But the judge noted Laycock's lack of prior criminal record, his good prospects of rehabilitation and the "public disgrace and humiliation" he had already gone through.

He also said that as a former policeman, Laycock would be at more risk in prison than other inmates.

Laycock will be in protective custody and will be eligible for parole in 2016.

ABC/AAP