But they agreed with Judge Susan Thomas' decision that he was not legally obliged to.
Police have not decided if they will appeal against the finding that Dalley was not guilty of criminal nuisance in not disclosing his HIV status but using a condom as a precaution.
In an earlier case, Dalley was found guilty of criminal nuisance and sentenced to 300 hours' community work for having unprotected sex with a previous partner.
The woman in that case, who has name suppression, has called for the law to be changed so disclosure is mandatory for people who are HIV-positive.
Some American states require people by law to disclose their HIV status before having sexual intercourse.
Caretaker Justice Minister Phil Goff said last night that there were no immediate plans for a law change. But he would listen to the public debate, and it might be an area that officials could work on.
Mr Goff said the case of deliberately not using protection and having intercourse was far more clear-cut.
Sexual health physician Dr Rick Franklin, of the Auckland Sexual Health Service, said his opinion was that a person should tell a sexual partner if they are HIV-positive, whether or not they used a condom.
He said an extreme position would be for everyone intending to have sexual intercourse to assume their partner was HIV-positive and take precautions.
Victoria University criminal law specialist Fran Wright said that although it would be morally right to tell a person, the use of a condom did make a difference and she believed the ruling was correct.