Serial sex offender and convicted murderer Malcolm Rewa's pleaded guilty to another historical rape - from behind bars

The 72-year-old's already serving an indefinite prison term for raping more than 20 women, and the 1992 murder of Susan Burdett.

Today Rewa appeared in the High Court at Auckland via audio visual feed - where he admitted to sexually violating a woman in Auckland in 1988.

He'd previously pleaded not guilty to the charge.

He'll return to the court in person for sentencing in April.