NSW Attorney-General Greg Smith is seeking a special guideline judgment in the appeal case of convicted one-punch killer Kieran Loveridge, which could be heard before a panel of five judges.

In a rare move, Mr Smith and the Director of Public Prosecutions are seeking a special judgment from the Court of Criminal Appeal, which would advise judges on how they should deal with other manslaughter cases, the court heard on Thursday.

Earlier this month, Loveridge was sentenced to at least four years for the manslaughter of 18-year-old Thomas Kelly in an unprovoked one punch attack in Kings Cross last year.

The DPP is appealing Loveridge's sentence on the grounds that it was manifestly inadequate.

Registrar Michael Crompton was told both the DPP and the attorney-general wished to be heard before a five-judge panel as they seek to apply for a guideline judgment.