Oscar Pistorius murder trial: key questions as defence begins

Potentially facing life in prison, Oscar Pistorius will likely take the stand this week as a witness in his own defence.

Pistorius is on trial for the murder of Reeva Steenkamp, his 29-year-old girlfriend, whom he shot four times at close distance while she was locked inside his bedroom washroom on Valentines Day last year. Pistorius says he fired in self-defence because he believed his model girlfriend was a home invader.

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The prosecution has made its case against Pistorius. During the trials first four weeks, the Pretoria court has heard dramatic testimony from neighbours who heard terrifying screaming and whose guts told them a family murder had taken place. It relived the moment first responders came upon Pistorius one of the worlds most recognizable athletes cradling her bleeding body. And it heard graphicdetails of the injuries Steenkamp suffered.

Here are some of the questions that will dominate the defence's case, which starts Monday with testimony from forensic pathologist Jan Botha:

Why did he shoot?

Above all, Pistorius needs to prove he acted lawfully in self-defence when he opened fire. Chief prosecutor Gerrie Nel will likely ask him tough but simple questions like why he didnt ask who was locked in the toilet before firing his handgun through the closed door.

Earlier, the prosecution sought to make Pistorius appear trigger happy, pointing to a night before Steenkamps shooting when Pistorius drew his gun and went into combat mode because of the sound of a laundry machine.

There are also the other gun charges, including one in which Pistorius stands accused of accidentally discharging a handgun in a crowded restaurant.

Pistoriuss defence must tread a fine line. It needs to show the runner was both a careful gun owner Sean Rens, manager of the International Firearm Training Academy, testified about training Pistorius earlier in the trial and someonewho had reason to feel at risk.

Why Pistorius felt like he was truly in danger is up to him to explain.

Will he keep his composure?

At various points in the trial, Pistorius has hung his head, cried, and even vomited as details of Steenkamps death were replayed. He has also turned red, stared intently at the proceedings, and scribbled notes.

His demeanour on the stand couldspeak volumes.

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Through text messages, internet search history and testimony related to other gun charges laid against Pistorius, the prosecution has painted the Olympian as a gun lover with a short temper whose web interests include fast cars and pornography.

In one message to Pistorius, read aloud in court, Steenkamp said: "I'm scared of u sometimes and how u snap at me."

The defence countered by pointing out dozens of affectionate messages, as well as CCTV footage showing the couple stealing a kiss in a convenience store.

But will that, plus Pistoriuss remaining Olympic shine, be enough to convince the court he's innocent?

Can the prosecution match the defence?

Almost every detail in the Pistorius trial from the screams (male or female? How many? How often?) to the gunshots (where was Steenkamp hit first?) has been contested.

Pistoriuss lawyer, Barry Roux, has asked each witness a twisting, complex series of questions. Some witnesses have stumbled under the questioning, allowing doubt to creep into their recollections of the night of the murder.

Now, Nel will get his chance to pick at Pistoriuss story.

Did police botch the investigation?

The Pistorius trial has been embarrassing for South African police. Their own crime scene photos showed officers moved evidence at the crime scene an obvious no-no and that one of Pistoriuss watches may have been stolen.

One officer, Col. G.S. van Rensburg, testified that he was very angry with how some officers handled themselves at the crime scene.

Its unlikely the case will be dismissed because of the police mistakes, but they could play arole in the trial's outcome.

What will the judge do?

And now to the trials most unknowable aspect. Whats going through the mind of Judge Thokozile Masipa?

Because South Africa has no jury trials, Masipa alone will decide Pistoriuss fate.

Masipa, a former crime reporter turned judge of the Gauteng Division of the High Court of South Africa, has presided over the trial with a calm poker face. Aside from rebuking Roux once for a line of questioning, and shaming a local broadcaster for televising the image of a witness, Masipa and her two assessors have quietly observed the prosecution and now await the defence.

One option for Masipa would be to convict Pistorius on a lesser charge, perhaps culpable homicide South Africas version of manslaughter.

If Masipa finds Pistorius guilty of premeditated murder, he faces life in prison.