Blood-curdling scream alerted neighbour

There was a "blood-curdling scream" and then Parwinder Kaur's neighbour saw her engulfed in flames from the neck down with her husband immediately behind her, a prosecutor has told a Sydney jury.

Kulwinder Singh, 41, has pleaded not guilty to murdering his wife Ms Kaur, 32, in December 2013.

She sustained burns to 90 per cent of her body in the petrol-fuelled blaze at their Rouse Hill home.

The Crown alleges Singh was responsible for her death but he told police she had set herself on fire while he was upstairs getting clothes to take to his mother's - he claims he didn't know where she was in the house at the time.

Crown prosecutor Chris Maxwell QC on Wednesday made his closing address to the NSW Supreme Court jury.

"He lit her and at the time he intended by doing that to kill her or cause her really serious bodily injury," he told the jurors.

The Crown's case is that Singh was downstairs when his wife was set on fire.

The jury was shown footage again from Singh's interview with police where he described hearing his wife's first scream - which he says he heard while upstairs.

Mr Maxwell then took the jury to evidence given by the couple's neighbour Tracey Valle who previously told the trial she had heard a "blood-curdling scream" and had looked out her window as a result.

"I saw my neighbour Parwinder on fire from the neck down," Mr Maxwell read out from her testimony.

Mr Maxwell said Ms Valle said she saw Singh "immediately behind" his burning wife.

He anticipated the defence would argue Ms Valle may have been mistaken.

However, Mr Maxwell noted Ms Valle had said a number of times that she had seen Singh on the driveway behind his wife immediately after hearing the scream.

As a result, he argued the jury "would reject out of hand he didn't know where she was during the time because for him to be on the driveway means that he had been downstairs before he heard that first scream".

The trial continues before Justice Natalie Adams.