Karen Ashcroft Maryborough alleged murder: Ben Wardlaw trial in Melbourne's Supreme Court

There's no doubt Ben Wardlaw, a man staying at the house, fatally stabbed her, his lawyer Malcolm Thomas told Wardlaw's murder trial in the Supreme Court in Melbourne on Thursday.

But he's told a jury Wardlaw's intentions when he stabbed Karen Ashcroft are in question and they must decide beyond reasonable doubt that he intended to kill or really seriously injure her or "whether his mental state was far from having that intention".

Ms Ashcroft, 52, died at a Maryborough home on May 14 last year after attending a gathering at a friend's house.

Crown prosecutor Diana Piekusis QC said people at the property were drinking and using drugs.

Ms Piekusis said Wardlaw, then 39, didn't speak to Ms Ashcroft at the house and didn't have anything to do with her at all that night - until she headed for the front door to go home.

"The accused, holding an orange hunting knife, approached Karen Ashcroft and stabbed her ... the knife went through her heart," she said.

The jury heard those gathered at the house described Wardlaw as having a blank expression and an "angry scowl" after the stabbing, while one man confronted him and took him outside.

"I had to. You've got to help me," Ms Piekusis said Wardlaw told the man.

Wardlaw was arrested in a nearby street hours later. Blood tests found he had methamphetamine, amphetamine and diazepam in his system.

Mr Thomas said there was no doubt Ms Ashcroft died because of Wardlaw's actions, and that he was responsible for her death but it was for the jury to decide whether prosecutors could prove beyond reasonable doubt he had committed murder, or whether to convict him of the lesser offence of manslaughter.

"What was in that man's mind at the instant, at the moment of that strike?" he said was what the jury had to decide. -AAP