Olympic and Paralympic track star Oscar Pistorius, centre, arrives at the High Court in Pretoria on Monday. Picture: Siphiwe Sibeko

Pretoria - A cell phone expert has shed light on the relationship of Oscar Pistorius and Reeva Steenkamp, revealing the athlete's extremely jealous side.

The second witness on the stand on Monday was Captain Francois Moller, a cellular phone expert who analysed the data on Oscar Pistorius and Reeva Steenkamp's cellular phones.

These phones were both found on the scene and others later handed over to the state after Pistorius shot and killed Steenkamp.

Two iPhones, two blackberry phones, two iPads and a Macbook Pro were all examined by police.

Moller said he removed the SIM cards from the two phones seized from the scene, and went through Pistorius' list of previously dialled numbers.

After examining the phones, he was able to determine one belonged to Pistorius, but that there was still another handset outstanding after examining Pistorius' billing records.

These blackberry's were later handed over. Moller was able to extract a huge amount of data from the phones, and it would have taken thousands of pages to print it out.

These included WhatsApp messages, texts and call logs, as well as all online data and even deleted messages.

Moller said 2731 messages on Steenkamp's phone were read through by investigators, and he printed the messages that applied to the case.

Using the phones' one of a kind serial or International Mobile Equipment Identifier numbers (IMEI) he was able to determine the senders and receivers of the messages found on the phones.

Prosecutor Gerrie Nel confirmed that Moller's in-depth analysis software meant no one could tamper with the information on the phone. One of the more than 1700 messages between the pair read to the court was:

"Angel, please don't say a thing to anyone. Darren told everyone it was his fault." This message from the athlete was most likely referring to the incident at the Tasha's restaurant where Pistorius accidentally discharged a firearm. His friend, Darren Fresco told management he had discharged the gun because Pistorius had asked us to.

A short while later, Steenkamp responded: "I don't know what you're talking about", followed by a smiling emoticon.

Less than a month before the shooting, Pistorius and Steenkamp had another text conversation.

The pair were arguing over Pistorius' serial dating, and how when she brought up an incident where she smoked marijuana with an ex-boyfriend, he had gotten upset.

"I'm scared of you sometimes. Of how you snap at me and react to me," she wrote.

She also defended herself from Pistorius' suggestion she had been flirting with a friend at a party, and how she wouldn't because it was her friend's husband.

"We are living in a double standards relationship," she wrote.

"I do everything to make you happy, you do everything to throw tantrums," she continued.

She revealed that Pistorius had scolded her for chewing gum and touching his neck.

"I am the girl who let go for you, even when I was scared out of my mind. I'm the girl who loves you."

But Pistorius sent back a lengthy apology. "I want to talk to you and sort this out. I don't want to have anything less than amazing for you and I," he wrote.

Another argument was also read to the court where Pistorius apologised for getting upset with Steenkamp for talking to another man.

He then also apologised for driving too fast after leaving the event, saying he was upset and hungry.

However, Moller also told the court that 90 percent of the conversations were "loving".

Earlier, defence advocate Kenny Oldwadge spent most of the morning trying to point out a series of contradictions in the testimony of one Of Pistorius' neighbours, Anette Stipp.

Stipp and her husband were woken up by gunshots and screams coming from Pistorius' home on the night he shot and killed Reeva Steenkamp.

Stipp began her testimony by telling the court she was suffering from flu on that night, and woke up just after 3am because of a bout of coughing.

She heard loud shot-like noises coming from the house.

Then she looked out of her bedroom window, and saw one of Pistorius' lights was on.

In Pistorius' ball affidavit, he said he'd only turned on the lights after firing the shots through the bathroom door.

When the screaming began, she got off the bed to look towards their bedroom balcony.

The sounds of screaming continued as they checked, and she assumed it was the sound of a "family murder".

Her husband said he wanted to find out what had happened in case any children were involved or anyone needed treatment.

By around 3.15am she heard more shots, coming from the home as her husband tried to get ready and call security.

But Oldwadge found a major inconsistency between Stipp's written police statement and her testimony in court. The statement said that after the shots, from her balcony she saw a man walking in the bathroom. But in court she said this was incorrect, as only her husband had seen the man.

Stipp said she had signed an incorrect police station where she said she'd seen a man walk across the bathroom.

She admitted the error and said she'd been the one to point this out to the prosecution. She was also unable to give details on her husbands calls to security on the night.

Oldwadge tried to argue the second bangs were the sound of a cricket bat hitting the bathroom door when Pistorius tried to break through it, but Stipp said the quick succession of the noises made this hard to believe.

Oldwadge also asked to look at Stipp's wrist watch, and present it to the court.

He then presented a photo of the Stipp's bedroom and the hand and wrist holding open the curtain for the police photographer. She admitted that was her hand - and her watch.

Earlier she had said she was not in the room when police were conducting their investigation.

She said she didn't remember why she was holding the curtain, or why she had been in the room.

She admitted that memory could be fallible, which Oldwadge had been trying to argue throughout his cross-examination.

Oldwadge then returned to the sounds of the two sets of bangs she heard, asking if the second set was softer than the first.

But she insisted that they sounded very similar, almost exactly the same.

The trial continues on Tuesday.

The Star