The Crown says a Dunedin cleaner beat his boss to death after dragging her out of a vehicle in which she tried to escape.
But Alexander James William Merritt's lawyer argued there was no evidence he was even at the Strathallan St premises of Spotless Cleaning Services when the fatal attack on 51-year-old Karin Ann Ross took place on December 2 last year.
Defence counsel Anne Stevens said her client, who has been on trial before the High Court at Dunedin for more than two weeks, was an "easy target" for police because he had clashed with the victim at work.
"Police decided early on it was Mr Merritt," she told the jury. "He was their suspect when they looked for their evidence."
But Crown prosecutor Robin Bates told the court in his closing address there was more than enough evidence for the jury to be sure of the 21-year-old's guilt.
He said the attack against Ross was "unrelenting". With more than 14 blows to her head and 32 defensive wounds to her hands and arms, the killer's intent was clear, Bates said.
Her blood in a van, which was found crashed into the skip, showed she had tried to escape and the prosecutor pointed to a bloody, gloved hand print which allegedly was left when Merritt dragged her out of the van and closed the door before continuing the frenzied attack.
Stevens said the blood at the scene had not been tested and was highly critical of the police's assumption that it all belonged to Ross.
"If the investigation was done properly we may know about someone else there."
Hair found in the hands of the victim was also untested, she said.
The Crown linked the crime scene to what officers found in a wheelie bin outside the Merritt family's home on Nairn St two days after the incident; a hammer, glove and a hoodie covered in Ross' blood.
Bates said testing of the top showed DNA from two sources extremely likely to be the victim and Merritt.
But the defence said the test was unreliable and the defendant's DNA could have been transferred to the garment from pizza boxes and drink bottles also in the bin.
Justice Nicholas Davidson will sum up the case this morning before the jury of eight men and four women retire to consider their verdict.