In Adelaide Magistrates Court on Monday Abigail Rebecca Foulkes admitted one count of deceiving another to gain a benefit.

The plea came after Harrap also pleaded guilty last week.

He admitted two counts of deception in relation to the use of his government car and to one count of conspiring to commit an abuse of public office.

Prosecutors dropped a fourth charge of conspiring to pervert the course of justice.

Harrap's early pleas mean he will be eligible for a discount of 40 per cent on any sentence imposed when he comes before the District Court in September.

Ms Foulkes will also face the District Court at the same time for sentencing submissions.

The deception charges related to misrepresentations Harrap made as to who was driving his car when it committed traffic offences in March and April this year.

It was alleged in both cases Harrap benefited by avoiding demerit points and a possible loss of his licence.

Another woman has also pleaded guilty in relation to that offence.

The conspiracy charge against Harrap related to a court case he presided over, though no further details have been revealed in court.

Lawyer Catherine Jayne Moyse was jointly charged on that count and has also admitted the offending.

Harrap remains free on bail and made no comment outside court.

He has been on leave since the charges were laid last month and recently quit his position with the Courts Administration Authority.

That resignation will take effect on August 10.

After his investigation and before Harrap's first court appearance, Independent Commissioner Against Corruption Bruce Lander took what he described as the unusual step of naming him.

Mr Lander explained "not naming the judicial officer would harm the confidence the community necessarily places in the judicial system".

Australian Associated Press