Aimee (R), sister of Olympic and Paralympic track star Oscar Pistorius is seen chatting to Reeva Steenkamp's mother,June (L) as her long time firend Jenny Strydom looks on ahead of Pistorius' murder trial at the North Gauteng High Court in Pretoria, Monday, 17 March 2014. Pistorius is on trial for murdering his girlfriend Reeva Steenkamp at his suburban Pretoria home on Valentine's Day last year. He says he mistook her for an intruder. Picture: Siphiwe Sibeko/Reuters/Pool

Pretoria - Murder-accused Oscar Pistorius's sister Aimee handed a letter to Reeva Steenkamp's mother, June, before the start of the 13th day of his trial in the North Gauteng High Court in Pretoria on Wednesday.

June Steenkamp arrived in court shortly before 9am, wearing a black-and-white photo of her daughter on the lapel of her white jacket.

She greeted three members of the ANC Women's League sitting in the front row of the public gallery and sat down next to them.

Pistorius arrived a few minutes later and walked past her. He nodded at her but she did not look at him.

Pistorius's sister Aimee sat down next to one of the ANCWL members and handed her a note, which was passed on to June Steenkamp.

She read it and looked up in the direction of Pistorius.

Moments before the two siblings had stood together writing the note.

On Tuesday, police ballistics expert Captain Christian Mangena told the court during questioning by prosecutor Gerrie Nel that he used the post-mortem report and police photographs to reconstruct the scene of Reeva Steenkamp's killing.

Pistorius shot his girlfriend through the locked toilet door in his Silver Woods Country Estate townhouse, apparently thinking she was an intruder.

Mangena testified how he used a laser and steel rods inserted into the four bullet holes in the door to determine the angle of the shots.

The holes are clustered on the right side of the door, under the keyhole.

They have been marked with white stickers with the letters A to D.

The Paralympic athlete has been charged with premeditated murder and contraventions of the Firearms Control Act.

He allegedly fired a shot from a Glock pistol under a table at a Johannesburg restaurant in January 2013.

On September 30, 2012, he allegedly shot through the open sunroof of a car with his 9mm pistol while driving with friends in Modderfontein.