UPDATED 5.27pm A 21-year-old Dunedin cleaner has been found guilty of murdering his 51-year-old work supervisor Karin Ross last year. 

Ms Ross’ body was found in the early hours on the second of December, in the carpark of Spotless cleaning, where they both worked.

According to pathologist Dr Michael Sage,Ms Ross suffered a number of injuries, including 14 lacerations to her head, and 32 defensive bruises to her hands and arms.

The jury consisting of eight men and four women deliberated for five hours before returning their verdict.

Merritt was remanded in custody by Justice Nicholas Davidson, and will appear at a later date for sentencing.

Earlier, Crown prosecutors Robin Bates and Richard Smith argued that Merritt, who was 20 at the time, travelled to Spotless Cleaning services and struck Ms Ross numerous times with a hammer between 1am and 2am on December 2. The Crown said Ms Ross attempted to flee in the company van, but was pulled out of the van by Merritt.

This was disputed by the defense, who argued that it could have been anyone who murdered Ms Ross given the open location of the dimly-lit crime scene. Counsels Anne Stevens and Alistair Logan said the incident took place at around 12.49am, when Ms Ross failed to take a call from Mrs Merritt about a new contract. They argued Merritt was asleep at the time of the attack.

The trial, which lasted almost two-and-a-half weeks, called on a number of different expert witnesses on behalf of the Crown prosecutors Robin Bates and Richard Smith.

Spark compliance expert Lawrence Watson was brought to discuss Merritt’s cellphone movements in the hours leading up to and after Ms Ross’ death. Watson told the court that Merritt’s phone had not accessed the two closest cellphone towers closest to his Nairn Street home at the time of the attack, therefore implying that the accused’s phone wasn’t at home.

Under cross-examination, Watson admitted to defense counsel Alistair Logan that the phone also did not register at the two cellphone towers closest to the Strathallan Street crime scene.

The court also heard from pathologist Dr Martin Sage, who confirmed that Ms Ross died from internal bleeding, as a result of blunt force trauma to her head.

Institute for Environment and Scientific Research (ESR) scientist Stephanie Opperman stated that blood found in Merritt’s bathroom was one trillion times more likely to have come from Ms Ross, than a random member of the public.

Fellow forensic scientist Timothy Power said the YSTR DNA found under Ms Ross’ right hand fingernails was 430 times more likely to have come from Merritt, than a random member of the public. Both cases, the Crown argued, showed strong scientific support that blood on some of Merritt’s items, including his shoes, belonged to Ms Ross.

Mrs Stevens disputed the DNA evidence, and criticised the small YTSR database of around 4500 people who had accessed the criminal justice system.

The accused’s mother and father, Sharon and Richard Merritt, also gave evidence throughout the two-week trial. Mrs Merritt, who also worked at Spotless cleaning as a night manager, spoke about discovering her colleague’s body at around 2am on December 2.