PRETORIA (AFP) - Paralympian Oscar Pistorius's murder trial starts its fourth week on Monday, with the state expected to start wrapping up its case.

The 27-year-old athlete disputes charges of premeditated murder, and says he only shot dead his girlfriend Reeva Steenkamp on February 14, 2013, because he mistook her for an intruder.

Here are highlights of the trial so far:

Witnesses

Four neighbours testified hearing a woman screaming and one hearing arguing voices in the dead of night on Valentines' Day last year.

University lecturer Michelle Burger heard "petrified screaming before the gunshots, and just after the gunshots".

Burger also described a pause between the first and second of the four shots.

The defence denies there was an argument and claims that the high-pitched screaming was actually Pistorius, who sounds like a woman when he is anxious.

Security guard Pieter Baba testified that Pistorius told him "everything is fine" in a phone conversation after the shooting. The defence disputes the wording, and presented records that showed Pistorius phoned Baba first, who denies this.

Two friends and an ex-girlfriend testified on unrelated charges, depicting the Paralympic gold medallist as hot-headed and obsessed with guns.

According to them, Pistorius always carried a gun with him, fired a gun through a moving car's open sunroof and another time in a crowded restaurant, then asked a friend to take the blame. Pistorius denies the incident in the car ever happened and said the gun in the restaurant went off by accident.

Police ballistics expert Captain Chris Mangena testified that the 29-year-old Steenkamp's wounds indicate she was standing and facing the locked toilet door when the first shot fractured her hip bone, and one of the next three hit her head.

This seems to support the state's case that she had time to scream before the fatal shot, as well as Burger's testimony about the firing sequence.

The defence argues a "double-tap" scenario, that the burst of four gunshots was too quick for the model to scream and alert her boyfriend she was in the toilet.

Evidence

In a case where the accused is the only other person at the scene, the broken toilet door with four gunshot holes is the main evidence. The holes suggest the athlete's height and distance from the door when he fired his 9 millimetre Parabellum pistol. The closer he was to the door, the more likely he approached it to get a clear shot of his target.

The door also shows marks where he broke down the panels with a cricket bat to get to the fatally wounded model. Pistorius says he broke down the door after shooting Steenkamp. His lawyers say police missed a mark on the door where he kicked trying to break it down.

A broken bedroom door, damaged bathroom tiles and a bent metal plate against the bath contradict the athlete's version that all was calm the night before the shooting.

Blood spots were also found on the duvet and on the wall behind the bed - out of the path the athlete would take while carrying his wounded girlfriend downstairs.

Cellphone records will shed more light on the calls made before and after the shooting.

Pistorius

The Paralympian broke down, sobbing loudly and retching repeatedly during graphic testimony and images showing Steenkamp's wounds. Dressed in a dark suit and sometimes wearing glasses, he looked down when the court was shown photos of his blood-spattered house.

During witness testimony he often wrote notes which he passed to his defence team, and sometimes read a book while underlining passages.

What lies ahead?

The state will call its last "four or five" witnesses from Monday and may close its case early in the week.

Pistorius himself is likely to take the stand in his defence to testify about events from that night. His lawyers will also call experts Pistorius enlisted to suggest different bullet trajectories that they say will confirm Steenkamp was hit after going to the toilet.

The defence will also try to show how police misconduct and incompetence contaminated evidence against him, and missed evidence that could support his version.