The star witness at a Dunedin murder trial has back-tracked on evidence he gave yesterday

Venod Skantha is on trial in the High Court - charged with murdering 16-year-old Amber-Rose Rush.

But defence lawyer Jonathan Eaton QC suggests the Crown's young witness is actually the one who killed her.

Yesterday, the teen told the court he was roped into driving Skantha to Amber-Rose's home the night she died - and explicitly remembered cleaning the bloody knife afterwards.

Now he says he can't remember whether he or Skantha cleaned it.