Two Department of Corrections officers say a man on remand at a Christchurch prison told them he murdered his former girlfriend by drowning her.
Nikki Roper is accused of murdering Christchurch mother Alexsis Tovizi at her home in Stanmore Road in December 2010, taking her car and laptop and using her eftpos card.
The 24-year-old has denied all charges at the High Court in Christchurch.
The Crown says Mr Roper killed MsTovizi with a military-style sleeper hold because he was jealous of her new boyfriend.
One of the officers, Geoff White, told the court on Friday they were taking round library books to inmates at Christchurch Men's Prison, when he and his colleague Luke Jenner started making small talk with Nikki Roper.
Mr White said Mr Roper told them police thought Alexsis Tovizi's death was caused by an overdose or natural causes, but in fact he drowned her.
Mr Jenner told the court he was surprised when Nikki Roper said he had drowned her.
A former prison inmate, who can't be named for legal reasons, gave evidence that Nikki Roper told him he had used a 'sleeper hold' on Ms Tovizi, because she was cheating on him.
For the defence, Simon Shamy asked the former inmate if he had made up the conversation in an attempt to get bail, but the man replied that wasn't true.
The trial will resume on Monday morning.