The 16-year-old, who has name suppression, was due to stand trial for the murder and sexual violation by unlawful sexual connection of the 22-year-old next month.
But he made a surprise appearance at the Timaru High Court sitting at Christchurch today to admit the charges.
The youth was 15 when he killed Ms Solomona at her Cass St home in Ashburton on December 15 last year.
He made a brief appearance in the dock to quietly utter "guilty" to both charges.
The teenager hung his head while other legal discussions were held.
Defence counsel Elizabeth Bulger asked for interim name suppression to continue, at least until sentencing.
Justice Graham Panckhurst agreed, even though he accepted it was "an unusual move" to continue name suppression after a guilty plea has been entered.
"This, however, is an unusual case, firstly, on account of your age - 16 years - and on account of the circumstances of the offending."
Justice Panckhurst also said the statement of facts should not be read out in court until sentencing, when the facts of the case and killer's identity will be revealed.
He will call for reports and remanded him in custody until sentencing at the High Court in Timaru on February 14.
Outside court, mother Amuella Solomona said: "I'm just happy that he's admitted it. It took him 10 months to do it."
The youth's family would not comment as they left court.
